Encoding and decoding a picture

ABSTRACT

An apparatus for decoding a picture is configured to partition the picture into coding blocks, using recursive multi-tree splitting. Splitting schemes for the multi-tree splitting are described. According to an embodiment, the decoder decodes a split direction flag from a data stream by context adaptive entropy decoding using a context which depends on whether, and discriminates be-tween, a first number of criteria which would be fulfilled in case of a split direction indicated by the split direction flag being horizontal equals a second number of criteria which would be fulfilled in case of the split direction indicated by the split direction flag being vertical, the first number being greater than the second number, and the first number being smaller than the second number.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a continuation of copending InternationalApplication No. PCT/EP2019/087169, filed Dec. 30, 2019, which isincorporated herein by reference in its entirety, and additionallyclaims priority from European Application No. EP 19150105.5, filed Jan.2, 2019, which is incorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

Embodiments of the current disclosure relate to the field of encodingand decoding a picture, such as in the field of image or video coding.In particular, embodiments relate to a partitioning tree design and itscoding in hybrid video compression, such as in the field of block basedimage or video coding.

In hybrid video coding, pictures are typically partitioned into smallervariable-sized blocks by which an adaptation to the characteristics ofthe input video signal can be achieved, which eventually increases thecompression efficiency. The partitioning into variable-sized blocks istypically represented by tree structures, such as quadtree, binary treeetc. The associated signaling depends on the chosen tree structure andhas an impact on the compression efficiency.

In state-of-the-art hybrid video coding, such as the High-EfficiencyVideo Coding (HEVC) standard, the input pictures are initiallydecomposed into disjoint square blocks of a fixed size. Each of thesefixed sized square blocks forms the root of a partitioning tree and canbe further subdivided into smaller blocks. The blocks that correspond tothe leaves of the partitioning tree are used for prediction andtransform coding. For these variable-size blocks, the original signal isoften predicted; the difference between the original and the predictionsignal is referred to as residual signal. The residual signal istransmitted using transform coding. In HEVC, the video pictures areinitially partitioned into square blocks, which are referred to asCoding Tree Units (CTUs) and each of the CTUs forms the root of apartitioning tree. HEVC uses quadtree structures for the subdivisioninto smaller units. At the leaves of the quadtree, the final blocks arereferred to as Coding Units (CUs). Each CU forms the root nodes for twofurther partitioning trees: one for the prediction parameters andanother for the transform coding stage. An important property ofquadtree structures is that the partitioning syntax element consists ofa single bin only. It signals whether or not a current block is splitinto four equal sized and disjoint blocks; therefore, it is alsoreferred to as a split flag. FIG. 1 illustrates the consequence of asingle split to the partitioning tree and the result in thetwo-dimensional picture. The split syntax element is coded in theregular mode of a context-based adaptive entropy coding engine (HEVCuses Context-Based Adaptive Arithmetic Coding, CABAC). Specifically, anadaptive context model is used for coding this syntax element. Thecontext modeling process for the split syntax element of the quadtreeemploys data on the quadtree depths of the current node and the alreadytransmitted partitioning trees of neighboring blocks. One out of threeavailable context models is chosen depending on the depths of theneighboring partitioning trees; the following three cases aredistinguished: (a) both neighboring depths are greater or equal to thecurrent depth, (b) both neighboring depths are smaller than the currentdepth, and (c) all other configurations.

In the latest video coding standardization activity of the ITU-T andISO/IEC, referred to as Versatile Video Coding (VVC), non-square blockshapes are used. Two alternative partitioning trees have beenincorporated into the existing quadtree design: binary and ternarytrees. As their name implies, a node can be split into two or threerectangular shapes. Those split shapes are interchangeable, and form afurther split tree themselves, a binary-ternary-tree (BTT).

For example, block-based image/video coding and context modelling forcontent prediction are used for compression of image or video data.

SUMMARY

An embodiment may have an apparatus for decoding a picture, configuredto

partition the picture into coding blocks using recursive multi-treesplitting depending on splitting information signaled in a data stream,

decode the picture from coding information which is signaled in the datastream and relates to the coding blocks,

wherein the apparatus is configured to partition the picture into thecoding blocks depending on splitting information signaled in a datastream by

-   -   decoding a split flag and a quad flag of the splitting        information from the data stream, wherein the split flag        indicates whether a predetermined block of the picture is to be        split or not to be split thereby stopping the recursive        multi-tree splitting with the predetermined block becoming one        of the coding blocks, and the quad flag indicates whether the        predetermined block of the picture is to be split into four        child blocks or not,    -   if the predetermined block of the picture is to be split, but        not to be split into four child blocks,        -   decoding a split direction flag from the data stream which            indicates whether the predetermined block of the picture is            to be split vertically or horizontally, if neither a second            nor a third predetermined criterion is fulfilled,        -   inferring that the split direction flag indicates that the            predetermined block of the picture is to be split            vertically, if the second predetermined criterion is            fulfilled, and        -   inferring that the split direction flag indicates that the            predetermined block of the picture is to be split            horizontally, if the third predetermined criterion is            fulfilled,        -   decoding a triple flag from the data stream which indicates            whether the predetermined block of the picture is to be            split into three child blocks or into two child blocks, if a            fourth predetermined criterion is not fulfilled, and        -   inferring that the triple flag indicates that the            predetermined block of the picture is to be split into two            child blocks, if the fourth predetermined criterion is            fulfilled, and that the triple flag indicates that the            predetermined block of the picture is to be split into three            child blocks and suppress the decoding of the triple flag            from the data stream, if a fifth predetermined criterion is            fulfilled,    -   if the predetermined block of the picture is to be split,        -   resuming the recursive multi-tree splitting for the child            blocks using even further flags of the splitting            information,

decode the split direction flag from the data stream by context adaptiveentropy decoding using a second context which depends on whether, anddiscriminates between,

-   -   a first number of criteria among the fourth and fifth        predetermined criteria which would be fulfilled in case of a        split direction indicated by the split direction flag being        horizontal equals a second number of criteria among the fourth        and fifth predetermined criteria which would be fulfilled in        case of the split direction indicated by the split direction        flag being vertical,    -   the first number being greater than the second number, and    -   the first number being smaller than the second number.

Another embodiment may have an apparatus for decoding a picture,configured to

partition the picture into coding blocks using recursive multi-treesplitting depending on splitting information signaled in a data stream,

decode the picture from coding information which is signaled in the datastream and relates to the coding blocks,

wherein the apparatus is configured to partition the picture into thecoding blocks depending on splitting information signaled in a datastream by

-   -   decoding a split flag and a quad flag of the splitting        information from the data stream, wherein the split flag        indicates whether a predetermined block of the picture is to be        split or not to be split thereby stopping the recursive        multi-tree splitting with the predetermined block becoming one        of the coding blocks, and the quad flag indicates whether the        predetermined block of the picture is to be split into four        child blocks or not,    -   if the predetermined block of the picture is to be split, but        not to be split into four child blocks,        -   decoding a split direction flag from the data stream which            indicates whether the predetermined block of the picture is            to be split vertically or horizontally, if neither a second            nor a third predetermined criterion is fulfilled,        -   inferring that the split direction flag indicates that the            predetermined block of the picture is to be split            vertically, if the second predetermined criterion is            fulfilled, and        -   inferring that the split direction flag indicates that the            predetermined block of the picture is to be split            horizontally, if the third predetermined criterion is            fulfilled,        -   decoding a triple flag from the data stream which indicates            whether the predetermined block of the picture is to be            split into three child blocks or into two child blocks, if a            fourth predetermined criterion is not fulfilled, and        -   inferring that the triple flag indicates that the            predetermined block of the picture is to be split into two            child blocks, if the fourth predetermined criterion is            fulfilled,    -   if the predetermined block of the picture is to be split,        -   resuming the recursive multi-tree splitting for the child            blocks using even further flags of the splitting            information,

decode the split direction flag from the data stream by context adaptiveentropy decoding using a second context which depends on whether, anddiscriminates between,

-   -   the fourth predetermined criterion would not neither be        fulfilled in case of a split direction indicated by the split        direction flag being horizontal nor in case of the split        direction indicated by the split direction flag being vertical        or be fulfilled both in case of a split direction indicated by        the split direction flag being horizontal as well as in case of        the split direction indicated by the split direction flag being        vertical,    -   the fourth predetermined criterion would be fulfilled in case of        the split direction indicated by the split direction flag being        horizontal and not be fulfilled in case of the split direction        indicated by the split direction flag being vertical, and    -   the fourth predetermined criterion would not be fulfilled in        case of the split direction indicated by the split direction        flag being horizontal and be fulfilled in case of the split        direction indicated by the split direction flag being vertical.

Yet another embodiment may have an apparatus for encoding a picture,configured to

partition the picture into coding blocks using recursive multi-treesplitting and encode splitting information defining the partitioning ina data stream,

encode the picture into coding information which is signaled in the datastream and relates to the coding blocks and encode the codinginformation in the data stream,

wherein the apparatus is configured to partition the picture into thecoding blocks depending on splitting information signaled in a datastream by

-   -   encoding a split flag and a quad flag of the splitting        information into the data stream, wherein the split flag        indicates whether a predetermined block of the picture is to be        split or not to be split thereby stopping the recursive        multi-tree splitting with the predetermined block becoming one        of the coding blocks, and the quad flag indicates whether the        predetermined block of the picture is to be split into four        child blocks or not,    -   if the predetermined block of the picture is to be split, but        not to be split into four child blocks,        -   encoding a split direction flag into the data stream which            indicates whether the predetermined block of the picture is            to be split vertically or horizontally, if neither a second            nor a third predetermined criterion is fulfilled,        -   suppress the encoding of the split direction flag if the            second predetermined criterion is fulfilled wherein same is            to be inferred to indicate that predetermined block of the            picture is to be split vertically, if the second            predetermined criterion is fulfilled, and        -   suppress the encoding of the split direction flag if the            third predetermined criterion is fulfilled wherein same is            to be inferred to indicate that the predetermined block of            the picture is to be split horizontally, if the third            predetermined criterion is fulfilled,        -   encoding a triple flag into the data stream which indicates            whether the predetermined block of the picture is to be            split into three child blocks or into two child blocks, if            fourth and fifth predetermined criteria are not fulfilled,            and        -   suppress the encoding the triple flag if the fourth            predetermined criterion is fulfilled wherein same is to be            inferred to indicate that the predetermined block of the            picture is to be split into two child blocks, if the fourth            predetermined criterion is fulfilled, and        -   suppress the encoding the triple flag if the fifth            predetermined criterion is fulfilled, wherein the triple            flag is to be inferred to indicate that the predetermined            block of the picture is to be split into three child blocks,            if the fifth predetermined criterion is fulfilled,    -   if the predetermined block of the picture is to be split,        -   resuming the encoding the splitting information for the            child blocks using even further flags of the splitting            information,

encode the split direction flag into the data stream by context adaptiveentropy encoding using a second context which depends on whether, anddiscriminates between,

-   -   a first number of criteria among the fourth and fifth        predetermined criteria which would be fulfilled in case of a        split direction indicated by the split direction flag being        horizontal equals a second number of criteria among the fourth        and fifth predetermined criteria which would be fulfilled in        case of the split direction indicated by the split direction        flag being vertical,    -   the first number being greater than the second number, and    -   the first number being smaller than the second number.

Yet another embodiment may have an apparatus for encoding a picture,configured to

partition the picture into coding blocks using recursive multi-treesplitting and encode splitting information defining the partitioning ina data stream,

encode the picture into coding information which relates to the codingblocks and encode the coding information in the data stream,

wherein the apparatus is configured to encode the splitting informationin the data stream by

-   -   encoding a split flag and a quad flag of the splitting        information into the data stream, wherein the split flag        indicates whether a predetermined block of the picture is to be        split or not to be split thereby stopping the recursive        multi-tree splitting with the predetermined block becoming one        of the coding blocks, and the quad flag indicates whether the        predetermined block of the picture is to be split into four        child blocks or not,    -   if the predetermined block of the picture is to be split, but        not to be split into four child blocks,        -   encoding a split direction flag into the data stream which            indicates whether the predetermined block of the picture is            to be split vertically or horizontally, if neither a second            nor a third predetermined criterion is fulfilled,        -   suppress the encoding of the split direction flag if the            second predetermined criterion is fulfilled wherein same is            to be inferred to indicate that predetermined block of the            picture is to be split vertically, if the second            predetermined criterion is fulfilled, and        -   suppress the encoding of the split direction flag if the            third predetermined criterion is fulfilled wherein same is            to be inferred to indicate that the predetermined block of            the picture is to be split horizontally, if the third            predetermined criterion is fulfilled,        -   encoding a triple flag into the data stream which indicates            whether the predetermined block of the picture is to be            split into three child blocks or into two child blocks, if a            fourth predetermined criterion is not fulfilled, and        -   suppress the encoding the triple flag if the fourth            predetermined criterion is fulfilled wherein same is to be            inferred to indicate that the predetermined block of the            picture is to be split into two child blocks, if the fourth            predetermined criterion is fulfilled,    -   if the predetermined block of the picture is to be split,        -   resuming the encoding of the splitting information for the            child blocks using even further flags of the splitting            information,

encode the split direction flag into the data stream by context adaptiveentropy encoding using a second context which depends on whether, anddiscriminates between,

-   -   the fourth predetermined criterion would not neither be        fulfilled in case of a split direction indicated by the split        direction flag being horizontal nor in case of the split        direction indicated by the split direction flag being vertical        or be fulfilled both in case of a split direction indicated by        the split direction flag being horizontal as well as in case of        the split direction indicated by the split direction flag being        vertical,    -   the fourth predetermined criterion would be fulfilled in case of        the split direction indicated by the split direction flag being        horizontal and not be fulfilled in case of the split direction        indicated by the split direction flag being vertical, and    -   the fourth predetermined criterion would not be fulfilled in        case of the split direction indicated by the split direction        flag being horizontal and be fulfilled in case of the split        direction indicated by the split direction flag being vertical.

According to an embodiment, a method for decoding a picture may have thesteps of:

partitioning the picture into coding blocks using recursive multi-treesplitting depending on splitting information signaled in a data stream,

decoding the picture from coding information which is signaled in thedata stream and relates to the coding blocks,

wherein the method includes partitioning the picture into the codingblocks depending on splitting information signaled in a data stream by

-   -   decoding a split flag and a quad flag of the splitting        information from the data stream, wherein the split flag        indicates whether a predetermined block of the picture is to be        split or not to be split thereby stopping the recursive        multi-tree splitting with the predetermined block becoming one        of the coding blocks, and the quad flag indicates whether the        predetermined block of the picture is to be split into four        child blocks or not,    -   if the predetermined block of the picture is to be split, but        not to be split into four child blocks,        -   decoding a split direction flag from the data stream which            indicates whether the predetermined block of the picture is            to be split vertically or horizontally, if neither a second            nor a third predetermined criterion is fulfilled,        -   inferring that the split direction flag indicates that the            predetermined block of the picture is to be split            vertically, if the second predetermined criterion is            fulfilled, and        -   inferring that the split direction flag indicates that the            predetermined block of the picture is to be split            horizontally, if the third predetermined criterion is            fulfilled,        -   decoding a triple flag from the data stream which indicates            whether the predetermined block of the picture is to be            split into three child blocks or into two child blocks, if a            fourth predetermined criterion is not fulfilled, and        -   inferring that the triple flag indicates that the            predetermined block of the picture is to be split into two            child blocks, if the fourth predetermined criterion is            fulfilled, and that the triple flag indicates that the            predetermined block of the picture is to be split into three            child blocks and suppress the decoding of the triple flag            from the data stream, if a fifth predetermined criterion is            fulfilled,    -   if the predetermined block of the picture is to be split,        -   resuming the recursive multi-tree splitting for the child            blocks using even further flags of the splitting            information,

decoding the split direction flag from the data stream by contextadaptive entropy decoding using a second context which depends onwhether, and discriminates between,

-   -   a first number of criteria among the fourth and fifth        predetermined criteria which would be fulfilled in case of a        split direction indicated by the split direction flag being        horizontal equals a second number of criteria among the fourth        and fifth predetermined criteria which would be fulfilled in        case of the split direction indicated by the split direction        flag being vertical,    -   the first number being greater than the second number, and    -   the first number being smaller than the second number.

According to another embodiment, a method for decoding a picture mayhave the steps of:

partitioning the picture into coding blocks using recursive multi-treesplitting depending on splitting information signaled in a data stream,

decoding the picture from coding information which is signaled in thedata stream and relates to the coding blocks,

wherein the method includes partitioning the picture into the codingblocks depending on splitting information signaled in a data stream by

-   -   decoding a split flag and a quad flag of the splitting        information from the data stream, wherein the split flag        indicates whether a predetermined block of the picture is to be        split or not to be split thereby stopping the recursive        multi-tree splitting with the predetermined block becoming one        of the coding blocks, and the quad flag indicates whether the        predetermined block of the picture is to be split into four        child blocks or not,    -   if the predetermined block of the picture is to be split, but        not to be split into four child blocks,        -   decoding a split direction flag from the data stream which            indicates whether the predetermined block of the picture is            to be split vertically or horizontally, if neither a second            nor a third predetermined criterion is fulfilled,        -   inferring that the split direction flag indicates that the            predetermined block of the picture is to be split            vertically, if the second predetermined criterion is            fulfilled, and        -   inferring that the split direction flag indicates that the            predetermined block of the picture is to be split            horizontally, if the third predetermined criterion is            fulfilled,        -   decoding a triple flag from the data stream which indicates            whether the predetermined block of the picture is to be            split into three child blocks or into two child blocks, if a            fourth predetermined criterion is not fulfilled, and        -   inferring that the triple flag indicates that the            predetermined block of the picture is to be split into two            child blocks, if the fourth predetermined criterion is            fulfilled,    -   if the predetermined block of the picture is to be split,        -   resuming the recursive multi-tree splitting for the child            blocks using even further flags of the splitting            information,

decoding the split direction flag from the data stream by contextadaptive entropy decoding using a second context which depends onwhether, and discriminates between,

-   -   the fourth predetermined criterion would not neither be        fulfilled in case of a split direction indicated by the split        direction flag being horizontal nor in case of the split        direction indicated by the split direction flag being vertical        or be fulfilled both in case of a split direction indicated by        the split direction flag being horizontal as well as in case of        the split direction indicated by the split direction flag being        vertical,    -   the fourth predetermined criterion would be fulfilled in case of        the split direction indicated by the split direction flag being        horizontal and not be fulfilled in case of the split direction        indicated by the split direction flag being vertical, and    -   the fourth predetermined criterion would not be fulfilled in        case of the split direction indicated by the split direction        flag being horizontal and be fulfilled in case of the split        direction indicated by the split direction flag being vertical.

According to yet another embodiment, a method for encoding a picture mayhave the steps of:

partitioning the picture into coding blocks using recursive multi-treesplitting and encoding splitting information defining the partitioningin a data stream,

encoding the picture into coding information which is signaled in thedata stream and relates to the coding blocks and encode the codinginformation in the data stream,

wherein the method includes partitioning the picture into the codingblocks depending on splitting information signaled in a data stream by

-   -   encoding a split flag and a quad flag of the splitting        information into the data stream, wherein the split flag        indicates whether a predetermined block of the picture is to be        split or not to be split thereby stopping the recursive        multi-tree splitting with the predetermined block becoming one        of the coding blocks, and the quad flag indicates whether the        predetermined block of the picture is to be split into four        child blocks or not,    -   if the predetermined block of the picture is to be split, but        not to be split into four child blocks,        -   encoding a split direction flag into the data stream which            indicates whether the predetermined block of the picture is            to be split vertically or horizontally, if neither a second            nor a third predetermined criterion is fulfilled,        -   suppressing the encoding of the split direction flag if the            second predetermined criterion is fulfilled wherein same is            to be inferred to indicate that predetermined block of the            picture is to be split vertically, if the second            predetermined criterion is fulfilled, and        -   suppressing the encoding of the split direction flag if the            third predetermined criterion is fulfilled wherein same is            to be inferred to indicate that the predetermined block of            the picture is to be split horizontally, if the third            predetermined criterion is fulfilled,        -   encoding a triple flag into the data stream which indicates            whether the predetermined block of the picture is to be            split into three child blocks or into two child blocks, if            fourth and fifth predetermined criteria are not fulfilled,            and        -   suppressing the encoding the triple flag if the fourth            predetermined criterion is fulfilled wherein same is to be            inferred to indicate that the predetermined block of the            picture is to be split into two child blocks, if the fourth            predetermined criterion is fulfilled, and        -   suppressing the encoding the triple flag if the fifth            predetermined criterion is fulfilled, wherein the triple            flag is to be inferred to indicate that the predetermined            block of the picture is to be split into three child blocks,            if the fifth predetermined criterion is fulfilled,    -   if the predetermined block of the picture is to be split,        -   resuming the encoding the splitting information for the            child blocks using even further flags of the splitting            information,

encoding the split direction flag into the data stream by contextadaptive entropy encoding using a second context which depends onwhether, and discriminates between,

-   -   a first number of criteria among the fourth and fifth        predetermined criteria which would be fulfilled in case of a        split direction indicated by the split direction flag being        horizontal equals a second number of criteria among the fourth        and fifth predetermined criteria which would be fulfilled in        case of the split direction indicated by the split direction        flag being vertical,    -   the first number being greater than the second number, and    -   the first number being smaller than the second number.

According to still another embodiment, a method for encoding a picturemay have the steps of:

partitioning the picture into coding blocks using recursive multi-treesplitting and encoding splitting information defining the partitioningin a data stream,

encoding the picture into coding information which relates to the codingblocks and encode the coding information in the data stream,

wherein the method includes encoding the splitting information in thedata stream by

-   -   encoding a split flag and a quad flag of the splitting        information into the data stream, wherein the split flag        indicates whether a predetermined block of the picture is to be        split or not to be split thereby stopping the recursive        multi-tree splitting with the predetermined block becoming one        of the coding blocks, and the quad flag indicates whether the        predetermined block of the picture is to be split into four        child blocks or not,    -   if the predetermined block of the picture is to be split, but        not to be split into four child blocks,        -   encoding a split direction flag into the data stream which            indicates whether the predetermined block of the picture is            to be split vertically or horizontally, if neither a second            nor a third predetermined criterion is fulfilled,        -   suppress the encoding of the split direction flag if the            second predetermined criterion is fulfilled wherein same is            to be inferred to indicate that predetermined block of the            picture is to be split vertically, if the second            predetermined criterion is fulfilled, and        -   suppressing the encoding of the split direction flag if the            third predetermined criterion is fulfilled wherein same is            to be inferred to indicate that the predetermined block of            the picture is to be split horizontally, if the third            predetermined criterion is fulfilled,        -   encoding a triple flag into the data stream which indicates            whether the predetermined block of the picture is to be            split into three child blocks or into two child blocks, if a            fourth predetermined criterion is not fulfilled, and        -   suppressing the encoding the triple flag if the fourth            predetermined criterion is fulfilled wherein same is to be            inferred to indicate that the predetermined block of the            picture is to be split into two child blocks, if the fourth            predetermined criterion is fulfilled,    -   if the predetermined block of the picture is to be split,        -   resuming the encoding of the splitting information for the            child blocks using even further flags of the splitting            information,

encoding the split direction flag into the data stream by contextadaptive entropy encoding using a second context which depends onwhether, and discriminates between,

-   -   the fourth predetermined criterion would not neither be        fulfilled in case of a split direction indicated by the split        direction flag being horizontal nor in case of the split        direction indicated by the split direction flag being vertical        or be fulfilled both in case of a split direction indicated by        the split direction flag being horizontal as well as in case of        the split direction indicated by the split direction flag being        vertical,    -   the fourth predetermined criterion would be fulfilled in case of        the split direction indicated by the split direction flag being        horizontal and not be fulfilled in case of the split direction        indicated by the split direction flag being vertical, and    -   the fourth predetermined criterion would not be fulfilled in        case of the split direction indicated by the split direction        flag being horizontal and be fulfilled in case of the split        direction indicated by the split direction flag being vertical.

Another embodiment may have a data stream encoded by any of theinventive method for encoding.

According to another embodiment, a non-transitory digital storage mediummay have a computer program stored thereon to perform any of theinventive methods when said computer program is run by a computer.

An aspect of the present disclosure concerns an apparatus for decoding apicture. The apparatus is configured to partition the picture intocoding blocks, for example tree leaf blocks, using recursive multi-treesplitting depending on splitting information signaled in a data stream.The apparatus is further configured to decode the picture from codinginformation which is signaled in the data stream and relates to thecoding blocks. The apparatus is configured to partition the picture intothe coding blocks depending on splitting information signaled in a datastream, e.g. the data stream, by decoding a split flag of the splittinginformation from the data stream which indicates whether a predeterminedblock of the picture is to be split or not to be split thereby stoppingthe recursive multi-tree splitting with the predetermined block becomingone of the coding blocks. That is, for example, if the split flagindicates that the predetermined block is not to be split, the recursivemulti-tree splitting is stopped. If the split flag indicates that thepredetermined block of the picture is to be split, the partitioning ofthe picture comprises decoding a quad flag of the splitting informationfrom the data stream which indicates whether the predetermined block ofthe picture is to be split into four child blocks or not. If the splitflag indicates that the predetermined block of the picture is to besplit, and if the quad flag indicates that the predetermined block ofthe picture is not to be split into four child blocks, the partitioningof the picture comprises decoding one or more further flags of thesplitting information from the data stream which indicate whether thepredetermined block of the picture is to be split into two or threechild blocks vertically or horizontally. Further, if the split flagindicates that the predetermined block of the picture is to be split,the partitioning of the picture comprises resuming the recursivemulti-tree splitting for the child blocks using even further flags ofthe splitting information. For example, in a further recursion of therecursive multi-tree splitting, one of the child blocks may be thepredetermined block. As the apparatus may stop the partitioning, if thesplit flag indicates that the predetermined block of the picture is tobe split, and as the apparatus may decode and/or evaluate the split flagbefore decoding a further flag, such as the quad flag, the apparatus mayonly decode one flag, namely the split flag, if the predetermined blockis not to be split further. Stopping the recursive partitioning afterdecoding of only one flag increases the decoding efficiency. Further, ifthe predetermined block is not to be split further, it may be sufficientto have the split flag in the splitting information, thus decreasing thesize of the data stream.

Another aspect concerns an apparatus for decoding a picture. Theapparatus is configured to partition the picture into coding blocksusing recursive multi-tree splitting depending on splitting informationsignaled in a data stream. The apparatus is further configured to decodethe picture from coding information which is signaled in the data streamand relates to the coding blocks. The apparatus is configured topartition the picture into the coding blocks depending on splittinginformation signaled in a data stream, e.g. the data stream, by decodinga split flag and a quad flag of the splitting information from the datastream. The split flag indicates whether a predetermined block of thepicture is to be split or not to be split thereby stopping the recursivemulti-tree splitting with the predetermined block becoming one of thecoding blocks. The quad flag indicates whether the predetermined blockof the picture is to be split into four child blocks or not. If thepredetermined block of the picture is to be split, but not to be splitinto four child blocks, the partitioning of the picture comprisesobtaining an information about a split direction flag and an informationabout a triple flag. The apparatus is configured to obtain theinformation about a split direction flag by decoding a split directionflag from the data stream which indicates whether the predeterminedblock of the picture is to be split vertically or horizontally, ifneither a second nor a third predetermined criterion is fulfilled. Ifthe second predetermined criterion is fulfilled, the apparatus isconfigured to obtain the information about a split direction flag byinferring that the split direction flag indicates that the predeterminedblock of the picture is to be split vertically. If the thirdpredetermined criterion is fulfilled, the apparatus is configured toobtain the information about a split direction flag by inferring thatthe split direction flag indicates that the predetermined block of thepicture is to be split horizontally. The apparatus is configured toobtain the information about a split direction flag by decoding a tripleflag from the data stream if a fourth predetermined criterion is notfulfilled. The triple flag indicates whether the predetermined block ofthe picture is to be split into three child blocks or into two childblocks. If the fourth predetermined criterion is fulfilled, theapparatus is configured to obtain the information about a splitdirection flag by inferring that the triple flag indicates that thepredetermined block of the picture is to be split into two child blocks.Further, if the predetermined block of the picture is to be split, thepartitioning of the picture comprises resuming the recursive multi-treesplitting for the child blocks using even further flags of the splittinginformation. The apparatus is further configured to decode the splitdirection flag from the data stream by context adaptive entropy decodingusing a second context. The second context depends on whether, anddiscriminates between a fulfillment of the following scenarios. In afirst scenario, the fourth predetermined criterion would not neither befulfilled in case of a split direction indicated by the split directionflag being horizontal nor in case of the split direction indicated bythe split direction flag being vertical or be fulfilled both in case ofa split direction indicated by the split direction flag being horizontalas well as in case of the split direction indicated by the splitdirection flag being vertical. In a second scenario, the fourthpredetermined criterion would be fulfilled in case of the splitdirection indicated by the split direction flag being horizontal and notbe fulfilled in case of the split direction indicated by the splitdirection flag being vertical. In a third scenario, the fourthpredetermined criterion would not be fulfilled in case of the splitdirection indicated by the split direction flag being horizontal and befulfilled in case of the split direction indicated by the splitdirection flag being vertical.

Another aspect concerns an apparatus for decoding a picture, configuredto partition the picture into coding blocks using recursive multi-treesplitting depending on splitting information signaled in a data stream.The apparatus is further configured to decode the picture from codinginformation which is signaled in the data stream and relates to thecoding blocks. The apparatus is configured to partition the picture intothe coding blocks depending on splitting information signaled in a datastream by decoding a split flag and a quad flag of the splittinginformation from the data stream. The split flag indicates whether apredetermined block of the picture is to be split or not to be split,the latter implying a stopping of the recursive multi-tree splittingwith the predetermined block becoming one of the coding blocks. The quadflag indicates whether the predetermined block of the picture is to besplit into four child blocks or not. If the predetermined block of thepicture is to be split, but not to be split into four child blocks theapparatus is configured for obtaining an information about a splitdirection flag and an information about a triple flag. Obtaining theinformation about a split direction flag comprises decoding a splitdirection flag from the data stream which indicates whether thepredetermined block of the picture is to be split vertically orhorizontally, if neither a second nor a third predetermined criterion isfulfilled. If the second predetermined criterion is fulfilled, obtainingthe information about a split direction flag comprises inferring thatthe split direction flag indicates that the predetermined block of thepicture is to be split vertically. If the third predetermined criterionis fulfilled, obtaining the information about a split direction flagcomprises inferring that the split direction flag indicates that thepredetermined block of the picture is to be split horizontally.Obtaining the information about a triple flag comprises decoding atriple flag from the data stream which indicates whether thepredetermined block of the picture is to be split into three childblocks or into two child blocks, if a fourth predetermined criterion isnot fulfilled. If the fourth predetermined criterion is fulfilled,obtaining the information about a triple flag comprises inferring thatthe triple flag indicates that the predetermined block of the picture isto be split into two child blocks. Further, if a fifth predeterminedcriterion is fulfilled, obtaining the information about a triple flagcomprises inferring that the triple flag indicates that thepredetermined block of the picture is to be split into three childblocks and suppressing the decoding of the triple flag from the datastream. If the predetermined block of the picture is to be split, thepartitioning of the picture comprises resuming the recursive multi-treesplitting for the child blocks using even further flags of the splittinginformation. Further, the apparatus if configured to decode the splitdirection flag from the data stream by context adaptive entropy decodingusing a second context. The second context depends on whether, anddiscriminates between, a first number of criteria among the fourth andfifth predetermined criteria being equal, greater and smaller than asecond number of criteria among the fourth and fifth predeterminedcriteria. The first number of criteria among the fourth and fifthpredetermined criteria would be fulfilled in case of a split directionindicated by the split direction flag being horizontal. The secondnumber of criteria among the fourth and fifth predetermined criteriawould be fulfilled in case of the split direction indicated by the splitdirection flag being vertical.

Another aspect concerns an apparatus for decoding a picture, configuredto partition the picture into coding blocks using recursive multi-treesplitting depending on splitting information signaled in a data stream.The apparatus is further configured to decode the picture from codinginformation which is signaled in the data stream and relates to thecoding blocks. The apparatus is configured to partition the picture intothe coding blocks depending on splitting information signaled in a datastream, e.g. the data stream, by decoding a split flag and a quad flagof the splitting information from the data stream. The split flagindicates whether a predetermined block of the picture is to be split ornot to be split thereby stopping the recursive multi-tree splitting withthe predetermined block becoming one of the coding blocks. The quad flagindicates whether the predetermined block of the picture is to be splitinto four child blocks or not. If the predetermined block of the pictureis to be split, but not to be split into four child blocks, thepartitioning of the picture comprises decoding a split direction flagfrom the data stream and decoding a triple flag from the data stream.The split direction flag indicates whether the predetermined block ofthe picture is to be split vertically or horizontally. The triple flagindicates whether the predetermined block of the picture is to be splitinto three child blocks or into two child blocks. If the predeterminedblock of the picture is to be split, the partitioning of the picturecomprises resuming the recursive multi-tree splitting for the childblocks using even further flags of the splitting information. Theapparatus is further configured to decode the triple flag from the datastream by context adaptive entropy decoding using a third context. Thethird context depends on a number of splits of the recursive multi-treesplitting, e.g. a number of recursions of the recursive multi-treesplitting, using which the predetermined block is obtained, or the thirdcontext depends on a size of the predetermined block. Alternatively oradditionally, the third context depends on whether, and discriminatesbetween the split direction flag indicating a horizontal splitdirection, and the split direction flag indicating a vertical splitdirection.

Another aspect concerns an apparatus for decoding a picture, configuredto partition the picture into coding blocks using recursive multi-treesplitting depending on splitting information signaled in a data stream.The apparatus if further configured to decode the picture from codinginformation which is signaled in the data stream and relates to thecoding blocks. The apparatus is configured to partition the picture intothe coding blocks depending on splitting information signaled in a datastream, e.g. the data stream, by decoding a split flag and a quad flagof the splitting information from the data stream. The split flagindicates whether a predetermined block of the picture is to be split ornot to be split thereby stopping the recursive multi-tree splitting withthe predetermined block becoming one of the coding blocks. The quad flagindicates whether the predetermined block of the picture is to be splitinto four child blocks or not. If the predetermined block of the pictureis to be split, but not to be split into four child blocks, partitioningthe picture comprises decoding one or more further flags of thesplitting information from the data stream which indicate whether thepredetermined block of the picture is to be split into two or threechild blocks vertically or horizontally. If the predetermined block ofthe picture is to be split, partitioning the picture comprises resumingthe recursive multi-tree splitting for the child blocks using evenfurther flags of the splitting information. The apparatus is furtherconfigured to select one of a first mode and a second mode. In the firstmode, the apparatus is configured to decode the quad flag after thesplit flag if the split flag indicates that the predetermined block ofthe picture is to be split. In the second mode, the apparatus ifconfigured to decode the split flag after the quad flag if the quad flagindicates that the predetermined child block of the picture is not to besplit into four child blocks.

Another aspect concerns an apparatus for encoding a picture. Theapparatus is configured to partition the picture into coding blocksusing recursive multi-tree splitting. The apparatus is configured toencode splitting information in a data stream, the splitting informationdefining the partitioning of the picture. The apparatus is furtherconfigured to encode the picture into coding information which relatesto the coding blocks and to encode the coding information in the datastream. The apparatus is configured to encode the splitting informationin the data stream by encoding a split flag of the splitting informationinto the data stream. The split flag indicates whether a predeterminedblock of the picture is to be split or not to be split thereby stoppingthe recursive multi-tree splitting with the predetermined block becomingone of the coding blocks. For example, the split flag may indicate to adecoder decoding the split flag, if the predetermined block is a codingblock, e.g. a tree leaf block, or if the predetermined block is furthersplit by another recursion of the recursive multi-tree splitting,thereby instructing the decoder to perform another such recursion. Ifthe split flag indicates that the predetermined block of the picture isto be split, the encoding of the splitting information comprisesencoding a quad flag of the splitting information into the data stream.The quad flag indicates whether the predetermined block of the pictureis to be split into four child blocks or not. If the split flagindicates that the predetermined block of the picture is to be split,and if the quad flag indicates that the predetermined block of thepicture is not to be split into four child blocks, the the encoding ofthe splitting information further comprises encoding one or more furtherflags of the splitting information into the data stream. The one or morefurther flags indicate whether the predetermined block of the picture isto be split into two or three child blocks vertically or horizontally.If the split flag indicates that the predetermined block of the pictureis to be split, the encoding of the splitting information furthercomprises resuming the encoding of the splitting information for thechild blocks using even further flags of the splitting information. Forexample, in a further recursion of the recursive multi-tree splitting,one of the child blocks may be the predetermined block.

Another aspect concerns an apparatus for encoding a picture, configuredto partition the picture into coding blocks using recursive multi-treesplitting and to encode splitting information defining the partitioningin a data stream. The apparatus is further configured to encode thepicture into coding information which relates to the coding blocks andencode the coding information in the data stream. The apparatus isconfigured to encode the splitting information in the data stream byencoding a split flag and a quad flag of the splitting information intothe data stream. The split flag indicates whether a predetermined blockof the picture is to be split or not to be split thereby stopping therecursive multi-tree splitting with the predetermined block becoming oneof the coding blocks. The quad flag indicates whether the predeterminedblock of the picture is to be split into four child blocks or not. Ifthe predetermined block of the picture is to be split, but not to besplit into four child blocks, and if neither a second nor a thirdpredetermined criterion is fulfilled, the encoding of the splittinginformation comprises encoding a split direction flag into the datastream. The split direction flag indicates whether the predeterminedblock of the picture is to be split vertically or horizontally. If thepredetermined block of the picture is to be split, but not to be splitinto four child blocks, and if the second predetermined criterion isfulfilled, the encoding of the splitting information comprisessuppressing the encoding of the split direction flag, wherein the splitdirection flag is to be inferred to indicate that the predeterminedblock of the picture is to be split vertically, if the secondpredetermined criterion is fulfilled. If the predetermined block of thepicture is to be split, but not to be split into four child blocks, andif the third predetermined criterion is fulfilled, the encoding of thesplitting information comprises suppressing the encoding of the splitdirection flag, wherein same is to be inferred to indicate that thepredetermined block of the picture is to be split horizontally, if thethird predetermined criterion is fulfilled. If the predetermined blockof the picture is to be split, but not to be split into four childblocks, and if a fourth predetermined criterion is not fulfilled, theencoding of the splitting information comprises encoding a triple flaginto the data stream. The triple flag indicates whether thepredetermined block of the picture is to be split into three childblocks or into two child blocks. If the predetermined block of thepicture is to be split, but not to be split into four child blocks, andif the fourth predetermined criterion is fulfilled, the encoding of thesplitting information comprises suppressing the encoding of the tripleflag, wherein same is to be inferred to indicate that the predeterminedblock of the picture is to be split into two child blocks, if the fourthpredetermined criterion is fulfilled. If the predetermined block of thepicture is to be split, the encoding of the splitting informationcomprises resuming the encoding of the splitting information for thechild blocks using even further flags of the splitting information. Theapparatus is further configured to encode the split direction flag intothe data stream by context adaptive entropy encoding using a secondcontext. The second context depends on whether, and discriminatesbetween a fulfillment of the following scenarios. In a first scenario,the fourth predetermined criterion would not neither be fulfilled incase of a split direction indicated by the split direction flag beinghorizontal nor in case of the split direction indicated by the splitdirection flag being vertical or be fulfilled both in case of a splitdirection indicated by the split direction flag being horizontal as wellas in case of the split direction indicated by the split direction flagbeing vertical. In a second scenario, the fourth predetermined criterionwould be fulfilled in case of the split direction indicated by the splitdirection flag being horizontal and not be fulfilled in case of thesplit direction indicated by the split direction flag being vertical. Ina third scenario, the fourth predetermined criterion would not befulfilled in case of the split direction indicated by the splitdirection flag being horizontal and be fulfilled in case of the splitdirection indicated by the split direction flag being vertical.

Another aspect concerns an apparatus for encoding a picture, configuredto partition the picture into coding blocks using recursive multi-treesplitting and encode splitting information defining the partitioning ina data stream. The apparatus is further configured to encode the pictureinto coding information which is signaled in the data stream and relatesto the coding blocks and encode the coding information in the datastream. The apparatus is configured to partition the picture into thecoding blocks depending on splitting information signaled in a datastream by encoding a split flag and a quad flag of the splittinginformation into the data stream. The split flag indicates whether apredetermined block of the picture is to be split or not to be splitthereby stopping the recursive multi-tree splitting with thepredetermined block becoming one of the coding blocks. The quad flagindicates whether the predetermined block of the picture is to be splitinto four child blocks or not. If the predetermined block of the pictureis to be split, but not to be split into four child blocks, and ifneither a second nor a third predetermined criterion is fulfilled, thepartitioning of the picture comprises encoding a split direction flaginto the data stream. The split direction flag indicates whether thepredetermined block of the picture is to be split vertically orhorizontally. If the predetermined block of the picture is to be split,but not to be split into four child blocks, and if neither a second nora third predetermined criterion is fulfilled, the partitioning of thepicture comprises suppressing the encoding of the split direction flagwherein same is to be inferred to indicate that predetermined block ofthe picture is to be split vertically, if the second predeterminedcriterion is fulfilled. If the predetermined block of the picture is tobe split, but not to be split into four child blocks, and if the thirdpredetermined criterion is fulfilled, the partitioning of the picturecomprises suppressing the encoding of the split direction flag, whereinsame is to be inferred to indicate that the predetermined block of thepicture is to be split horizontally, if the third predeterminedcriterion is fulfilled. If the predetermined block of the picture is tobe split, but not to be split into four child blocks, and if fourth andfifth predetermined criteria are not fulfilled, the partitioning of thepicture comprises encoding a triple flag into the data stream. Thetriple flag indicates whether the predetermined block of the picture isto be split into three child blocks or into two child blocks. If thepredetermined block of the picture is to be split, but not to be splitinto four child blocks, and if the fourth predetermined criterion isfulfilled, the partitioning of the picture comprises suppressing theencoding the triple flag, wherein same is to be inferred to indicatethat the predetermined block of the picture is to be split into twochild blocks, if the fourth predetermined criterion is fulfilled. If thepredetermined block of the picture is to be split, but not to be splitinto four child blocks, and if the fifth predetermined criterion isfulfilled, the partitioning of the picture comprises suppressing theencoding of the triple flag, wherein the triple flag is to be inferredto indicate that the predetermined block of the picture is to be splitinto three child blocks, if the fifth predetermined criterion isfulfilled. If the predetermined block of the picture is to be split, thepartitioning of the picture comprises

-   -   resuming the encoding the splitting information for the child        blocks using even further flags of the splitting information.        Further, the apparatus is configured to encode the split        direction flag into the data stream by context adaptive entropy        encoding using a second context which depends on whether, and        discriminates between a first number being equal, greater or        smaller than a second number. The first number is a first number        of criteria among the fourth and fifth predetermined criteria        which would be fulfilled in case of a split direction indicated        by the split direction flag being horizontal. The second number        is a second number of criteria among the fourth and fifth        predetermined criteria which would be fulfilled in case of the        split direction indicated by the split direction flag being        vertical.

Another aspect concerns an apparatus for encoding a picture, configuredto partition the picture into coding blocks using recursive multi-treesplitting and encode splitting information defining the partitioning ina data stream. Further, the apparatus is configured to encode thepicture into coding information which relates to the coding blocks andencode the coding information in the data stream. The apparatus isconfigured to encode the splitting information into the data stream byencoding a split flag and a quad flag of the splitting information intothe data stream, wherein the split flag indicates whether apredetermined block of the picture is to be split or not to be splitthereby stopping the recursive multi-tree splitting with thepredetermined block becoming one of the coding blocks, and the quad flagindicates whether the predetermined block of the picture is to be splitinto four child blocks or not. If the predetermined block of the pictureis to be split, but not to be split into four child blocks, the encodingof the splitting information comprises encoding a split direction flaginto the data stream and encoding a triple flag into the data stream.The split direction flag indicates whether the predetermined block ofthe picture is to be split vertically or horizontally. The triple flagindicates whether the predetermined block of the picture is to be splitinto three child blocks or into two child blocks. If the predeterminedblock of the picture is to be split, the encoding of the splittinginformation comprises resuming the encoding of the splitting informationfor the child blocks using even further flags of the splittinginformation. The apparatus is configured to encode the triple flag intothe data stream by context adaptive entropy encoding using a thirdcontext. The third context depends on a number of splits of therecursive multi-tree splitting using which the predetermined block isobtained, or the third context depends on a size of the predeterminedblock. Additionally or alternatively, the third context depends onwhether, and discriminates between, the split direction flag indicatinga horizontal split direction, and the split direction flag indicating avertical split direction.

Another aspect concerns an apparatus for encoding a picture, configuredto partition the picture into coding blocks using recursive multi-treesplitting and encode splitting information defining the partitioning ina data stream. The apparatus is further configured to encode the pictureinto coding information which relates to the coding blocks and encodethe coding information in the data stream. The apparatus is configuredto encode the splitting information into the data stream by encoding asplit flag and a quad flag of the splitting information into the datastream, wherein the split flag indicates whether a predetermined blockof the picture is to be split or not to be split thereby stopping therecursive multi-tree splitting with the predetermined block becoming oneof the coding blocks, and the quad flag indicates whether thepredetermined block of the picture is to be split into four child blocksor not. If the predetermined block of the picture is to be split, butnot to be split into four child blocks, the encoding of the splittinginformation comprises encoding one or more further flags of thesplitting information into the data stream which indicate whether thepredetermined block of the picture is to be split into two or threechild blocks vertically or horizontally. If the predetermined block ofthe picture is to be split, the encoding of the splitting informationcomprises resuming the encoding of the splitting information for thechild blocks using even further flags of the splitting information. Theapparatus is configured to select one of a first mode and a second mode.In the first mode, the apparatus is configured to encode the quad flagafter the split flag if the split flag indicates that the predeterminedblock of the picture is to be split. In the second mode, the apparatusis configured to encode the split flag after the quad flag if the quadflag indicates that the predetermined child block of the picture is notto be split into four child blocks.

Another aspect concerns a method for decoding a picture, comprising apartitioning of the picture 12′ into coding blocks using recursivemulti-tree splitting depending on splitting information signaled in adata stream, and further comprising a decoding the picture 12′ fromcoding information which is signaled in the data stream and relates tothe coding blocks. The method further comprises partitioning the picture12′ into the coding blocks depending on splitting information signaledin a data stream by decoding a split flag of the splitting informationfrom the data stream which indicates whether a predetermined block ofthe picture 12′ is to be split or not to be split thereby stopping therecursive multi-tree splitting with the predetermined block becoming oneof the coding blocks. If the split flag indicates that the predeterminedblock of the picture 12′ is to be split, the partitioning of the picturecomprises decoding a quad flag of the splitting information from thedata stream which indicates whether the predetermined block of thepicture 12′ is to be split into four child blocks or not. lif the quadflag indicates that the predetermined block of the picture 12′ is not tobe split into four child blocks, the partitioning of the picturecomprises decoding one or more further flags of the splittinginformation from the data stream which indicate whether thepredetermined block of the picture 12′ is to be split into two or threechild blocks vertically or horizontally. If the split flag indicatesthat the predetermined block of the picture 12′ is to be split, thepartitioning of the picture comprises resuming the recursive multi-treesplitting for the child blocks using even further flags of the splittinginformation.

Another aspect concerns a method for decoding a picture, comprising apartitioning of the picture 12′ into coding blocks using recursivemulti-tree splitting depending on splitting information signaled in adata stream. The method further comprises decoding the picture 12′ fromcoding information which is signaled in the data stream and relates tothe coding blocks. The method comprises partitioning the picture 12′into the coding blocks depending on splitting information signaled in adata stream by decoding a split flag and a quad flag of the splittinginformation from the data stream, wherein the split flag indicateswhether a predetermined block of the picture 12′ is to be split or notto be split thereby stopping the recursive multi-tree splitting with thepredetermined block becoming one of the coding blocks, and the quad flagindicates whether the predetermined block of the picture 12′ is to besplit into four child blocks or not. If the predetermined block of thepicture 12′ is to be split, but not to be split into four child blocks,the partitioning of the picture comprises decoding a split directionflag from the data stream which indicates whether the predeterminedblock of the picture 12′ is to be split vertically or horizontally, ifneither a second nor a third predetermined criterion is fulfilled. Ifthe predetermined block of the picture 12′ is to be split, but not to besplit into four child blocks, the partitioning of the picture comprisesinferring that the split direction flag indicates that the predeterminedblock of the picture 12′ is to be split vertically, if the secondpredetermined criterion is fulfilled. If the predetermined block of thepicture 12′ is to be split, but not to be split into four child blocks,the partitioning of the picture comprises inferring that the splitdirection flag indicates that the predetermined block of the picture 12′is to be split horizontally, if the third predetermined criterion isfulfilled. If the predetermined block of the picture 12′ is to be split,but not to be split into four child blocks, the partitioning of thepicture comprises decoding a triple flag from the data stream whichindicates whether the predetermined block of the picture 12′ is to besplit into three child blocks or into two child blocks, if a fourthpredetermined criterion is not fulfilled. If the predetermined block ofthe picture 12′ is to be split, but not to be split into four childblocks, the partitioning of the picture comprises inferring that thetriple flag indicates that the predetermined block of the picture 12′ isto be split into two child blocks, if the fourth predetermined criterionis fulfilled. If the predetermined block of the picture 12′ is to besplit, the partitioning of the picture comprises resuming the recursivemulti-tree splitting for the child blocks using even further flags ofthe splitting information. The method further comprises decoding thesplit direction flag from the data stream by context adaptive entropydecoding using a second context which depends on whether, anddiscriminates between, a and which of the following scenarios beingfulfilled: (i) the fourth predetermined criterion would not neither befulfilled in case of a split direction indicated by the split directionflag being horizontal nor in case of the split direction indicated bythe split direction flag being vertical or be fulfilled both in case ofa split direction indicated by the split direction flag being horizontalas well as in case of the split direction indicated by the splitdirection flag being vertical, (ii) the fourth predetermined criterionwould be fulfilled in case of the split direction indicated by the splitdirection flag being horizontal and not be fulfilled in case of thesplit direction indicated by the split direction flag being vertical,and (iii) the fourth predetermined criterion would not be fulfilled incase of the split direction indicated by the split direction flag beinghorizontal and be fulfilled in case of the split direction indicated bythe split direction flag being vertical.

Another aspect concerns a method for decoding a picture, comprising apartitioning of the picture 12′ into coding blocks using recursivemulti-tree splitting depending on splitting information signaled in adata stream, and further comprising decoding the picture 12′ from codinginformation which is signaled in the data stream and relates to thecoding blocks. The method comprises partitioning the picture 12′ intothe coding blocks depending on splitting information signaled in a datastream by decoding a split flag and a quad flag of the splittinginformation from the data stream, wherein the split flag indicateswhether a predetermined block of the picture 12′ is to be split or notto be split thereby stopping the recursive multi-tree splitting with thepredetermined block becoming one of the coding blocks, and the quad flagindicates whether the predetermined block of the picture 12′ is to besplit into four child blocks or not. If the predetermined block of thepicture 12′ is to be split, but not to be split into four child blocks,the partitioning of the picture comprises decoding a split directionflag from the data stream which indicates whether the predeterminedblock of the picture 12′ is to be split vertically or horizontally, ifneither a second nor a third predetermined criterion is fulfilled. Ifthe predetermined block of the picture 12′ is to be split, but not to besplit into four child blocks, the partitioning of the picture furthercomprises inferring that the split direction flag indicates that thepredetermined block of the picture 12′ is to be split vertically, if thesecond predetermined criterion is fulfilled. If the predetermined blockof the picture 12′ is to be split, but not to be split into four childblocks, the partitioning of the picture further comprises inferring thatthe split direction flag indicates that the predetermined block of thepicture 12′ is to be split horizontally, if the third predeterminedcriterion is fulfilled. If the predetermined block of the picture 12′ isto be split, but not to be split into four child blocks, thepartitioning of the picture further comprises decoding a triple flagfrom the data stream which indicates whether the predetermined block ofthe picture 12′ is to be split into three child blocks or into two childblocks, if a fourth predetermined criterion is not fulfilled. If thepredetermined block of the picture 12′ is to be split, but not to besplit into four child blocks, the partitioning of the picture furthercomprises inferring that the triple flag indicates that thepredetermined block of the picture 12′ is to be split into two childblocks, if the fourth predetermined criterion is fulfilled, and that thetriple flag indicates that the predetermined block of the picture 12′ isto be split into three child blocks and suppress the decoding of thetriple flag from the data stream, if a fifth predetermined criterion isfulfilled. If the predetermined block of the picture 12′ is to be split,the partitioning of the picture comprises resuming the recursivemulti-tree splitting for the child blocks using even further flags ofthe splitting information. Further, the method comprises decoding thesplit direction flag from the data stream by context adaptive entropydecoding using a second context which depends on whether, anddiscriminates between (i) a first number of criteria among the fourthand fifth predetermined criteria which would be fulfilled in case of asplit direction indicated by the split direction flag being horizontalequals a second number of criteria among the fourth and fifthpredetermined criteria which would be fulfilled in case of the splitdirection indicated by the split direction flag being vertical (ii) thefirst number being greater than the second number, and (iii) the firstnumber being smaller than the second number.

Another aspect concerns a method for decoding a picture, comprising apartitioning of the picture 12′ into coding blocks using recursivemulti-tree splitting depending on splitting information signaled in adata stream, and further comprising decoding the picture 12′ from codinginformation which is signaled in the data stream and relates to thecoding blocks. The method comprises partitioning the picture 12′ intothe coding blocks depending on splitting information signaled in a datastream by decoding a split flag and a quad flag of the splittinginformation from the data stream, wherein the split flag indicateswhether a predetermined block of the picture 12′ is to be split or notto be split thereby stopping the recursive multi-tree splitting with thepredetermined block becoming one of the coding blocks, and the quad flagindicates whether the predetermined block of the picture 12′ is to besplit into four child blocks or not. If the predetermined block of thepicture 12′ is to be split, but not to be split into four child blocks,the partitioning of the picture comprises decoding a split directionflag from the data stream which indicates whether the predeterminedblock of the picture 12′ is to be split vertically or horizontally, anddecoding a triple flag from the data stream which indicates whether thepredetermined block of the picture 12′ is to be split into three childblocks or into two child blocks. If the predetermined block of thepicture 12′ is to be split, the partitioning of the picture comprisesresuming the recursive multi-tree splitting for the child blocks usingeven further flags of the splitting information. The decoding of thetriple flag from the data stream by context adaptive entropy decodingcomprises using a third context which depends on a number of splits ofthe recursive multi-tree splitting using which the predetermined blockis obtained, or a size of the predetermined block. Additionally oralternatively, the third context depends on whether, and discriminatesbetween, the split direction flag indicating a horizontal splitdirection, and the split direction flag indicating a vertical splitdirection.

Another aspect concerns a method for decoding a picture, comprising apartitioning of the picture 12′ into coding blocks using recursivemulti-tree splitting depending on splitting information signaled in adata stream, and decoding the picture 12′ from coding information whichis signaled in the data stream and relates to the coding blocks. Themethod comprises partitioning the picture 12′ into the coding blocksdepending on splitting information signaled in a data stream by decodinga split flag and a quad flag of the splitting information from the datastream, wherein the split flag indicates whether a predetermined blockof the picture 12′ is to be split or not to be split thereby stoppingthe recursive multi-tree splitting with the predetermined block becomingone of the coding blocks, and the quad flag indicates whether thepredetermined block of the picture 12′ is to be split into four childblocks or not. If the predetermined block of the picture 12′ is to besplit, but not to be split into four child blocks, the partitioning ofthe picture comprises decoding one or more further flags of thesplitting information from the data stream which indicate whether thepredetermined block of the picture 12′ is to be split into two or threechild blocks vertically or horizontally. If the predetermined block ofthe picture 12′ is to be split, the partitioning of the picturecomprises resuming the recursive multi-tree splitting for the childblocks using even further flags of the splitting information. The methodfurther comprises selecting one of a first mode and a second mode, and,in the first mode, decoding the quad flag after the split flag if thesplit flag indicates that the predetermined block of the picture 12′ isto be split, and in the second mode, decoding the split flag after thequad flag if the quad flag indicates that the predetermined child blockof the picture 12′ is not to be split into four child blocks.

Another aspect concerns a method for encoding a picture, comprising apartitioning of the picture into coding blocks using recursivemulti-tree splitting and encoding splitting information defining thepartitioning in a data stream. The method further comprises encoding thepicture into coding information which relates to the coding blocks andencoding the coding information in the data stream. Further, the methodcomprises encoding the splitting information in the data stream byencoding a split flag of the splitting information into the data streamwhich indicates whether a predetermined block of the picture is to besplit or not to be split thereby stopping the recursive multi-treesplitting with the predetermined block becoming one of the codingblocks. If the split flag indicates that the predetermined block of thepicture is to be split, the partitioning of the picture comprisesencoding a quad flag of the splitting information into the data streamwhich indicates whether the predetermined block of the picture is to besplit into four child blocks or not. If the quad flag indicates that thepredetermined block of the picture is not to be split into four childblocks, the method comprises encoding one or more further flags of thesplitting information into the data stream which indicate whether thepredetermined block of the picture is to be split into two or threechild blocks vertically or horizontally. If the split flag indicatesthat the predetermined block of the picture is to be split, the methodcomprises resuming the encoding the splitting information for the childblocks using even further flags of the splitting information.

Another aspect concerns a method for encoding a picture, comprising apartitioning of the picture into coding blocks using recursivemulti-tree splitting and encoding splitting information defining thepartitioning in a data stream. The method further comprises encoding thepicture into coding information which relates to the coding blocks andencode the coding information in the data stream. Further, the methodcomprises encoding the splitting information in the data stream byencoding a split flag and a quad flag of the splitting information intothe data stream, wherein the split flag indicates whether apredetermined block of the picture is to be split or not to be splitthereby stopping the recursive multi-tree splitting with thepredetermined block becoming one of the coding blocks, and the quad flagindicates whether the predetermined block of the picture is to be splitinto four child blocks or not. If the predetermined block of the pictureis to be split, but not to be split into four child blocks, the methodcomprises encoding a split direction flag into the data stream whichindicates whether the predetermined block of the picture is to be splitvertically or horizontally, if neither a second nor a thirdpredetermined criterion is fulfilled. If the predetermined block of thepicture is to be split, but not to be split into four child blocks, themethod comprises suppressing the encoding of the split direction flag ifthe second predetermined criterion is fulfilled wherein same is to beinferred to indicate that predetermined block of the picture is to besplit vertically, if the second predetermined criterion is fulfilled. Ifthe predetermined block of the picture is to be split, but not to besplit into four child blocks, the method comprises suppressing theencoding of the split direction flag if the third predeterminedcriterion is fulfilled wherein same is to be inferred to indicate thatthe predetermined block of the picture is to be split horizontally, ifthe third predetermined criterion is fulfilled. If the predeterminedblock of the picture is to be split, but not to be split into four childblocks, the method comprises encoding a triple flag into the data streamwhich indicates whether the predetermined block of the picture is to besplit into three child blocks or into two child blocks, if a fourthpredetermined criterion is not fulfilled. If the predetermined block ofthe picture is to be split, but not to be split into four child blocks,the method comprises suppressing the encoding the triple flag if thefourth predetermined criterion is fulfilled wherein same is to beinferred to indicate that the predetermined block of the picture is tobe split into two child blocks, if the fourth predetermined criterion isfulfilled. If the predetermined block of the picture is to be split, themethod comprises resuming the encoding of the splitting information forthe child blocks using even further flags of the splitting information.The method further comprises encoding the split direction flag into thedata stream by context adaptive entropy encoding using a second contextwhich depends on whether, and discriminates between (i) the fourthpredetermined criterion would not neither be fulfilled in case of asplit direction indicated by the split direction flag being horizontalnor in case of the split direction indicated by the split direction flagbeing vertical or be fulfilled both in case of a split directionindicated by the split direction flag being horizontal as well as incase of the split direction indicated by the split direction flag beingvertical (ii) the fourth predetermined criterion would be fulfilled incase of the split direction indicated by the split direction flag beinghorizontal and not be fulfilled in case of the split direction indicatedby the split direction flag being vertical, (iii) the fourthpredetermined criterion would not be fulfilled in case of the splitdirection indicated by the split direction flag being horizontal and befulfilled in case of the split direction indicated by the splitdirection flag being vertical.

Another aspect concerns a method for encoding a picture, comprising apartitioning of the picture into coding blocks using recursivemulti-tree splitting and encoding splitting information defining thepartitioning in a data stream. Further, the method comprises encodingthe picture into coding information which is signaled in the data streamand relates to the coding blocks and encode the coding information inthe data stream. The method comprises partitioning the picture into thecoding blocks depending on splitting information signaled in a datastream by encoding a split flag and a quad flag of the splittinginformation into the data stream, wherein the split flag indicateswhether a predetermined block of the picture is to be split or not to besplit thereby stopping the recursive multi-tree splitting with thepredetermined block becoming one of the coding blocks, and the quad flagindicates whether the predetermined block of the picture is to be splitinto four child blocks or not. If the predetermined block of the pictureis to be split, but not to be split into four child blocks, the methodcomprises encoding a split direction flag into the data stream whichindicates whether the predetermined block of the picture is to be splitvertically or horizontally, if neither a second nor a thirdpredetermined criterion is fulfilled. If the predetermined block of thepicture is to be split, but not to be split into four child blocks, themethod comprises suppressing the encoding of the split direction flag ifthe second predetermined criterion is fulfilled wherein same is to beinferred to indicate that predetermined block of the picture is to besplit vertically, if the second predetermined criterion is fulfilled. Ifthe predetermined block of the picture is to be split, but not to besplit into four child blocks, the method comprises suppressing theencoding of the split direction flag if the third predeterminedcriterion is fulfilled wherein same is to be inferred to indicate thatthe predetermined block of the picture is to be split horizontally, ifthe third predetermined criterion is fulfilled. If the predeterminedblock of the picture is to be split, but not to be split into four childblocks, the method comprises encoding a triple flag into the data streamwhich indicates whether the predetermined block of the picture is to besplit into three child blocks or into two child blocks, if fourth andfifth predetermined criteria are not fulfilled. If the predeterminedblock of the picture is to be split, but not to be split into four childblocks, the method comprises suppressing the encoding the triple flag ifthe fourth predetermined criterion is fulfilled wherein same is to beinferred to indicate that the predetermined block of the picture is tobe split into two child blocks, if the fourth predetermined criterion isfulfilled. If the predetermined block of the picture is to be split, butnot to be split into four child blocks, the method comprises suppressingthe encoding the triple flag if the fifth predetermined criterion isfulfilled, wherein the triple flag is to be inferred to indicate thatthe predetermined block of the picture is to be split into three childblocks, if the fifth predetermined criterion is fulfilled. If thepredetermined block of the picture is to be split, the method comprisesresuming the encoding the splitting information for the child blocksusing even further flags of the splitting information. The methodcomprises an encoding of the split direction flag into the data streamby context adaptive entropy encoding using a second context whichdepends on whether, and discriminates between, (i) a first number ofcriteria among the fourth and fifth predetermined criteria which wouldbe fulfilled in case of a split direction indicated by the splitdirection flag being horizontal equals a second number of criteria amongthe fourth and fifth predetermined criteria which would be fulfilled incase of the split direction indicated by the split direction flag beingvertical, (ii) the first number being greater than the second number,and (iii) the first number being smaller than the second number.

Another aspect concerns a method for encoding a picture, comprising apartitioning of the picture into coding blocks using recursivemulti-tree splitting and encoding splitting information defining thepartitioning in a data stream. The method further comprises encoding thepicture into coding information which relates to the coding blocks andencode the coding information in the data stream. Further, the methodcomprises encoding the splitting information into the data stream byencoding a split flag and a quad flag of the splitting information intothe data stream, wherein the split flag indicates whether apredetermined block of the picture is to be split or not to be splitthereby stopping the recursive multi-tree splitting with thepredetermined block becoming one of the coding blocks, and the quad flagindicates whether the predetermined block of the picture is to be splitinto four child blocks or not. If the predetermined block of the pictureis to be split, but not to be split into four child blocks, methodcomprises encoding a split direction flag into the data stream whichindicates whether the predetermined block of the picture is to be splitvertically or horizontally, and encoding a triple flag into the datastream which indicates whether the predetermined block of the picture isto be split into three child blocks or into two child blocks. If thepredetermined block of the picture is to be split, the method comprisesresuming the encoding the splitting information for the child blocksusing even further flags of the splitting information. Further, themethod comprises encoding the triple flag into the data stream bycontext adaptive entropy encoding using a third context which depends ona number of splits of the recursive multi-tree splitting using which thepredetermined block is obtained, or a size of the predetermined block.Additionally or alternatively, the third context depends on whether, anddiscriminates between,

-   -   the split direction flag indicating a horizontal split        direction, and the split direction flag indicating a vertical        split direction.

Another aspect concerns a method for encoding a picture, comprising apartitioning of the picture into coding blocks using recursivemulti-tree splitting and encode splitting information defining thepartitioning in a data stream, and an encoding the picture into codinginformation which relates to the coding blocks and encode the codinginformation in the data stream. Further, the method comprises encodingthe splitting information into the data stream by encoding a split flagand a quad flag of the splitting information into the data stream,wherein the split flag indicates whether a predetermined block of thepicture is to be split or not to be split thereby stopping the recursivemulti-tree splitting with the predetermined block becoming one of thecoding blocks, and the quad flag indicates whether the predeterminedblock of the picture is to be split into four child blocks or not. Ifthe predetermined block of the picture is to be split, but not to besplit into four child blocks, the method comprises encoding one or morefurther flags of the splitting information into the data stream whichindicate whether the predetermined block of the picture is to be splitinto two or three child blocks vertically or horizontally. If thepredetermined block of the picture is to be split, the method comprisesresuming the encoding the splitting information for the child blocksusing even further flags of the splitting information. Further, themethod comprises selecting one of a first mode and a second mode, and,in the first mode, encoding the quad flag after the split flag if thesplit flag indicates that the predetermined block of the picture is tobe split, and in the second mode, encoding the split flag after the quadflag if the quad flag indicates that the predetermined child block ofthe picture is not to be split into four child blocks.

The methods rely on the same ideas as the devices described above,providing equal or equivalent functionalities and advantages. Themethods may optionally be combined with (or supplemented by) any of thefeatures, functionalities and details described herein with respect tothe corresponding device. The methods may optionally be combined withthe mentioned features, functionalities and details both individually orin any combination of them.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention will be detailed subsequentlyreferring to the appended drawings, in which:

FIG. 1 shows a schematic representation of an apparatus for encoding apicture, which may implement the disclosed concept,

FIG. 2 shows a schematic representation of an apparatus for decoding apicture, which may implement the disclosed concept,

FIG. 3 illustrates signals used by encoders or decoders according to anembodiment,

FIG. 4 shows a schematic representation of an apparatus for decoding apicture according to an embodiment,

FIG. 5 shows a schematic representation of an apparatus for decoding apicture according to a further embodiment,

FIG. 6 shows a schematic representation of an apparatus for decoding apicture according to a further embodiment,

FIG. 7 illustrates an exemplary embodiment of the second context,

FIG. 8 shows a schematic representation of an apparatus for decoding apicture according to a further embodiment,

FIG. 9 shows a schematic representation of an apparatus for decoding apicture according to a further embodiment,

FIGS. 10A, B illustrate a quadtree split according to an embodiment,

FIG. 11 illustrates a partitioning tree according to the current VVC,

FIG. 12 illustrates a partitioning tree according to an embodiment,

FIG. 13 shows a schematic representation of an apparatus for encoding apicture according to an embodiment,

FIG. 14 shows a flow chart of an embodiment of a method for decoding apicture,

FIG. 15 shows a flow chart of an embodiment of a method for decoding apicture,

FIG. 16 shows a flow chart of an embodiment of a method for decoding apicture,

FIG. 17 shows a flow chart of an embodiment of a method for decoding apicture,

FIG. 18 shows a flow chart of an embodiment of a method for decoding apicture,

FIG. 19 shows table 1,

FIG. 20 shows table 2,

FIG. 21 shows table 3,

FIG. 22 shows table 4,

FIG. 23 shows table 5.

DETAILED DESCRIPTION OF THE INVENTION

In the following, different inventive embodiments and aspects will bedescribed. Also, further embodiments will be defined by the enclosedclaims.

It should be noted that any embodiments as defined by the claims can besupplemented by any of the details (features and functionalities)described herein. Also, the embodiments described herein can be usedindividually, and can also optionally be supplemented by any of thedetails (features and functionalities) included in the claims. Also, itshould be noted that individual aspects described herein can be usedindividually or in combination. Thus, details can be added to each ofsaid individual aspects without adding details to another one of saidaspects. It should also be noted that the present disclosure describesexplicitly or implicitly features usable in encoding and decodingimages/videos. Thus, any of the features described herein can be used inthe context of encoding and decoding images/videos.

The invention will be understood more fully from the detaileddescription given below and from the accompanying drawings ofembodiments of the invention, which, however, should not be taken tolimit the invention to the specific embodiments described, but are forexplanation and understanding only.

The following description of the figures starts with a presentation of adescription of an encoder and a decoder of a block-based predictivecodec for coding pictures of a video in order to form an example for acoding framework into which embodiments of the present invention may bebuilt in. The respective encoder and decoder are described with respectto FIGS. 1 to 3. Thereinafter the description of embodiments of theconcept of the present invention is presented along with a descriptionas to how such concepts could be built into the encoder and decoder ofFIGS. 1 and 2, respectively, although the embodiments described with thesubsequent FIG. 4 and following, may also be used to form encoders anddecoders not operating according to the coding framework underlying theencoder and decoder of FIGS. 1 and 2.

FIG. 1 shows an apparatus for predictively coding a picture 12 into adata stream 14 exemplarily using transform-based residual coding. Theapparatus, or encoder, is indicated using reference sign 10. FIG. 2shows a corresponding decoder 20, i.e. an apparatus 20 configured topredictively decode the picture 12′ from the data stream 14 also usingtransform-based residual decoding, wherein the apostrophe has been usedto indicate that the picture 12′ as reconstructed by the decoder 20deviates from picture 12 originally encoded by apparatus 10 in terms ofcoding loss introduced by a quantization of the prediction residualsignal. FIG. 1 and FIG. 2 exemplarily use transform based predictionresidual coding, although embodiments of the present application are notrestricted to this kind of prediction residual coding. This is true forother details described with respect to FIGS. 1 and 2, too, as will beoutlined hereinafter.

The encoder 10 is configured to subject the prediction residual signalto spatial-to-spectral transformation and to encode the predictionresidual signal, thus obtained, into the data stream 14. Likewise, thedecoder 20 is configured to decode the prediction residual signal fromthe data stream 14 and subject the prediction residual signal thusobtained to spectral-to-spatial transformation.

Internally, the encoder 10 may comprise a prediction residual signalformer 22 which generates a prediction residual 24 so as to measure adeviation of a prediction signal 26 from the original signal, i.e. fromthe picture 12. The prediction residual signal former 22 may, forinstance, be a subtractor which subtracts the prediction signal from theoriginal signal, i.e. from the picture 12. The encoder 10 then furthercomprises a transformer 28 which subjects the prediction residual signal24 to a spatial-to-spectral transformation to obtain a spectral-domainprediction residual signal 24′ which is then subject to quantization bya quantizer 32, also comprised by the encoder 10. The thus quantizedprediction residual signal 24″ is coded into bitstream 14. To this end,encoder 10 may optionally comprise an entropy coder 34 which entropycodes the prediction residual signal as transformed and quantized intodata stream 14. The prediction signal 26 is generated by a predictionstage 36 of encoder 10 on the basis of the prediction residual signal24″ encoded into, and decodable from, data stream 14. To this end, theprediction stage 36 may internally, as is shown in FIG. 1, comprise adequantizer 38 which dequantizes prediction residual signal 24″ so as togain spectral-domain prediction residual signal 24′″, which correspondsto signal 24′ except for quantization loss, followed by an inversetransformer 40 which subjects the latter prediction residual signal 24′″to an inverse transformation, i.e. a spectral-to-spatial transformation,to obtain prediction residual signal 24″″, which corresponds to theoriginal prediction residual signal 24 except for quantization loss. Acombiner 42 of the prediction stage 36 then recombines, such as byaddition, the prediction signal 26 and the prediction residual signal24″″ so as to obtain a reconstructed signal 46, i.e. a reconstruction ofthe original signal 12. Reconstructed signal 46 may correspond to signal12′. A prediction module 44 of prediction stage 36 then generates theprediction signal 26 on the basis of signal 46 by using, for instance,spatial prediction, i.e. intra-picture prediction, and/or temporalprediction, i.e. inter-picture prediction.

Likewise, decoder 20, as shown in FIG. 2, may be internally composed ofcomponents corresponding to, and interconnected in a mannercorresponding to, prediction stage 36. In particular, entropy decoder 50of decoder 20 may entropy decode the quantized spectral-domainprediction residual signal 24″ from the data stream, whereupondequantizer 52, inverse transformer 54, combiner 56 and predictionmodule 58, interconnected and cooperating in the manner described abovewith respect to the modules of prediction stage 36, recover thereconstructed signal on the basis of prediction residual signal 24″ sothat, as shown in FIG. 2, the output of combiner 56 results in thereconstructed signal, namely picture 12′.

Although not specifically described above, it is readily clear that theencoder 10 may set some coding parameters including, for instance,prediction modes, motion parameters and the like, according to someoptimization scheme such as, for instance, in a manner optimizing somerate and distortion related criterion, i.e. coding cost. For example,encoder 10 and decoder 20 and the corresponding modules 44, 58,respectively, may support different prediction modes such asintra-coding modes and inter-coding modes. The granularity at whichencoder and decoder switch between these prediction mode types maycorrespond to a subdivision of picture 12 and 12′, respectively, intocoding segments or coding blocks. In units of these coding segments, forinstance, the picture may be subdivided into blocks being intra-codedand blocks being inter-coded. Intra-coded blocks are predicted on thebasis of a spatial, already coded/decoded neighborhood of the respectiveblock as is outlined in more detail below. Several intra-coding modesmay exist and be selected for a respective intra-coded segment includingdirectional or angular intra-coding modes according to which therespective segment is filled by extrapolating the sample values of theneighborhood along a certain direction which is specific for therespective directional intra-coding mode, into the respectiveintra-coded segment. The intra-coding modes may, for instance, alsocomprise one or more further modes such as a DC coding mode, accordingto which the prediction for the respective intra-coded block assigns aDC value to all samples within the respective intra-coded segment,and/or a planar intra-coding mode according to which the prediction ofthe respective block is approximated or determined to be a spatialdistribution of sample values described by a two-dimensional linearfunction over the sample positions of the respective intra-coded blockwith driving tilt and offset of the plane defined by the two-dimensionallinear function on the basis of the neighboring samples. Comparedthereto, inter-coded blocks may be predicted, for instance, temporally.For inter-coded blocks, motion vectors may be signaled within the datastream, the motion vectors indicating the spatial displacement of theportion of a previously coded picture of the video to which picture 12belongs, at which the previously coded/decoded picture is sampled inorder to obtain the prediction signal for the respective inter-codedblock. This means, in addition to the residual signal coding comprisedby data stream 14, such as the entropy-coded transform coefficientlevels representing the quantized spectral-domain prediction residualsignal 24″, data stream 14 may have encoded thereinto coding modeparameters for assigning the coding modes to the various blocks,prediction parameters for some of the blocks, such as motion parametersfor inter-coded segments, and optional further parameters such asparameters for controlling and signaling the subdivision of picture 12and 12′, respectively, into the segments. The decoder 20 uses theseparameters to subdivide the picture in the same manner as the encoderdid, to assign the same prediction modes to the segments, and to performthe same prediction to result in the same prediction signal.

FIG. 3 illustrates the relationship between the reconstructed signal,i.e. the reconstructed picture 12′, on the one hand, and the combinationof the prediction residual signal 24″″ as signaled in the data stream14, and the prediction signal 26, on the other hand. As already denotedabove, the combination may be an addition. The prediction signal 26 isillustrated in FIG. 3 as a subdivision of the picture area intointra-coded blocks which are illustratively indicated using hatching,and inter-coded blocks which are illustratively indicated not-hatched.The subdivision may be any subdivision, such as a regular subdivision ofthe picture area into rows and columns of square blocks or non-squareblocks, or a multi-tree subdivision of picture 12 from a tree rootblock, for example a CTU, into a plurality of leaf blocks of varyingsize, for example CUs. The subdivision may be any subdivision, such as aquadtree subdivision or a binary or ternary subdivision or the like,wherein a mixture thereof is illustrated in FIG. 3 in which the picturearea is first subdivided into rows and columns of tree root blocks whichare then further subdivided in accordance with a recursive multi-treesubdivisioning into one or more leaf blocks. Recursive multi-treesubdivisioning may also be referred to as recursive multi-treesplitting.

Again, data stream 14 may have an intra-coding mode coded thereinto forintra-coded blocks 80, which assigns one of several supportedintra-coding modes to the respective intra-coded block 80. Forinter-coded blocks 82, the data stream 14 may have one or more motionparameters coded thereinto. Generally speaking, inter-coded blocks 82are not restricted to being temporally coded. Alternatively, inter-codedblocks 82 may be any block predicted from previously coded portionsbeyond the current picture 12 itself, such as previously coded picturesof a video to which picture 12 belongs, or picture of another view or anhierarchically lower layer in the case of encoder and decoder beingscalable encoders and decoders, respectively.

The prediction residual signal 24″″ in FIG. 3 is also illustrated as asubdivision of the picture area into blocks 84. These blocks might becalled transform blocks in order to distinguish same from the codingblocks 80 and 82. In effect, FIG. 3 illustrates that encoder 10 anddecoder 20 may use two different subdivisions of picture 12 and picture12′, respectively, into blocks, namely one subdivisioning into codingblocks 80 and 82, respectively, and another subdivision into transformblocks 84. Both subdivisions might be the same, i.e. each coding block80 and 82, may concurrently form a transform block 84, but FIG. 3illustrates the case where, for instance, a subdivision into transformblocks 84 forms an extension of the subdivision into coding blocks 80,82 so that any border between two blocks of blocks 80 and 82 overlays aborder between two blocks 84, or alternatively speaking each block 80,82 either coincides with one of the transform blocks 84 or coincideswith a cluster of transform blocks 84. However, the subdivisions mayalso be determined or selected independent from each other so thattransform blocks 84 could alternatively cross block borders betweenblocks 80, 82. As far as the subdivision into transform blocks 84 isconcerned, similar statements are thus true as those brought forwardwith respect to the subdivision into blocks 80, 82, i.e. the blocks 84may be the result of a regular subdivision of picture area into blocks(with or without arrangement into rows and columns), the result of arecursive multi-tree subdivisioning (or recursive multi-tree splitting)of the picture area, or a combination thereof or any other sort ofblockation. Just as an aside, it is noted that blocks 80, 82 and 84 arenot restricted to being of quadratic, rectangular or any other shape.

FIG. 3 further illustrates that the combination of the prediction signal26 and the prediction residual signal 24″″ directly results in thereconstructed signal 12′. However, it should be noted that more than oneprediction signal 26 may be combined with the prediction residual signal24″″ to result into picture 12′ in accordance with alternativeembodiments.

In FIG. 3, the transform blocks 84 shall have the followingsignificance. Transformer 28 and inverse transformer 54 perform theirtransformations in units of these transform blocks 84. For instance,many codecs use some sort of DST or DCT for all transform blocks 84.Some codecs allow for skipping the transformation so that, for some ofthe transform blocks 84, the prediction residual signal is coded in thespatial domain directly. However, in accordance with embodimentsdescribed below, encoder 10 and decoder 20 are configured in such amanner that they support several transforms. For example, the transformssupported by encoder 10 and decoder 20 could comprise:

-   -   DCT-II (or DCT-III), where DCT stands for Discrete Cosine        Transform    -   DST-IV, where DST stands for Discrete Sine Transform    -   DCT-IV    -   DST-VII    -   Identity Transformation (IT)

Naturally, while transformer 28 would support all of the forwardtransform versions of these transforms, the decoder 20 or inversetransformer 54 would support the corresponding backward or inverseversions thereof:

-   -   Inverse DCT-II (or inverse DCT-III)    -   Inverse DST-IV    -   Inverse DCT-IV    -   Inverse DST-VII    -   Identity Transformation (IT)

The subsequent description provides more details on which schemes forsubdivisioning or partitioning or splitting tree root blocks into one ormore leaf blocks may be supported by the encoder 10 and the decoder 20.For example, these splitting schemes may provide means for obtaining thecoding blocks 80, 82 and/or the transform blocks 84, 84 a.

FIGS. 10A and 10B illustrate an example for a quadtree split and theresulting nodes, for example child blocks. FIG. 10A depicts thepartitioning tree where a node A is further split into four nodes. FIG.10B depicts the result on the partitioning where the block A issubdivided into four disjoint and equal sized blocks. For example, thesplitting of the node A into the four nodes B, C, D, E as shown in FIGS.10A and 10B may represent a splitting of a parent block into childblocks, as may be performed by one recursion of a recursive multi-treesplitting.

The partitioning as shown in FIGS. 10A and 10B may be appliedrecursively. That is, for example, the partitioning may partition aparent block into one or more child blocks, of which a child block mayserve as the parent block for a further recursion of the partitioning.For example, a tree root block may be partitioned multiple times forobtaining one or more leaf blocks. For example, different tree leafblocks may have been obtained by a different or same number ofrecursions of different or same types of partitioning, so that a formand a size of different tree leaf blocks may differ from each other. Thenumber of recursions of partitioning for obtaining a specific block ofthe picture may, for example, be referred to as a tree depth of thespecific block.

A scheme for splitting a parent block into a child block may compriseinformation about whether to split or not to split a parent block andinformation about how to split a parent block. Such a scheme may beillustrated by a partitioning tree.

FIG. 11 illustrates a partitioning tree 1100, e.g. a rule for splittinga parent block 1111 into one or more child blocks 1112, of the currentVVC development having nested binary and ternary partitioning trees. Inaddition to the existing blocks, e.g. blocks known from previous codecs,resulting from quadtree splits, further rectangular shapes can berepresented, e.g. by the partitioning tree 1100. A deviation from thequadtree can occur when the quadtree split flag is equal to zero. Abinary-ternary-tree starts in the quad-tree leaf-nodes, for example ifthe quad-tree split flag indicates to not split the parent block 1111into four child blocks. The binary-ternary-tree forms a recursivesplitting tree, similarly to the quad-tree, but with different splitswhich might be applied at each node, e.g. each parent block, e.g. if theparent block is not split into four child blocks. Also, depending onspecific node properties such as size, position or tree depth, not allsplits are available at every node. Only flags that cannot be inferredbased on already available data need to be transmitted. When themtt_split_flag is either signaled or inferred to be equal to zero, thepartitioning tree is terminated at this node (i.e., the correspondingnode represents a leaf node and the associated block is used forprediction and transform coding).

As denoted in FIG. 2, up to four syntax elements may be used to specifythe final CU shape. No further subdivision may use at least two syntaxelements (qt_split_flag equal to 0 and mtt_split_flag equal to 0) inthis scheme. The context modeling for the qt_split_flag is similar tothe approach used in HEVC. The quadtree depth of the current node iscompared to the final quadtree depths of the neighboring coding trees(the neighbor above the current block and the neighbor left to thecurrent block). Furthermore, a separate context model set is used whenthe current quadtree depth is greater than one. Instead of the quadtreedepth, the width and the height of the current node is compared relativeto the width of the above and the height of the left neighbors for themtt_split_flag. Three different context model sets are used depending onthe current CU size for the luma component, whereas a dedicated contextmodel set is used for the chroma components. Note that the current VVCdraft allows different partitioning trees for luma and chroma when theslice type is intra, i.e., when the prediction inside the currentpicture (or slice or tile) is restricted to intra-picture predictiononly.

The mtt_split_vertical_flag involves three context models depending onthe aspect ratio of the current node:a context model for the case wherethe node is a square block, another for the case where the width isgreater than the height, and a third for the opposite case. In contrast,a single context model is used for the mtt_split_binary_flag.

As already outlined above, FIGS. 1 to 3 have been presented as anexample where the inventive concept described further below may beimplemented in order to form specific examples for encoders and decodersaccording to the present application. Insofar, the encoder and decoderof FIGS. 1 and 2, respectively, may represent possible implementationsof the encoders and decoders described herein below. FIGS. 1 and 2 are,however, only examples. An encoder according to embodiments of thepresent application may, however, perform block-based encoding of apicture 12 using the concept outlined in more detail below and beingdifferent from the encoder of FIG. 1 such as, for instance, in that sameis no video encoder, but a still picture encoder, in that same does notsupport inter-prediction, or in that the sub-division into blocks 80 isperformed in a manner different than exemplified in FIG. 3. Likewise,decoders according to embodiments of the present application may performblock-based decoding of picture 12′ from data stream 14 using the codingconcept further outlined below, but may differ, for instance, from thedecoder 20 of FIG. 2 in that same is no video decoder, but a stillpicture decoder, in that same does not support intra-prediction, or inthat same sub-divides picture 12′ into blocks in a manner different thandescribed with respect to FIG. 3 and/or in that same does not derive theprediction residual from the data stream 14 in transform domain, but inspatial domain, for instance.

FIG. 4 illustrates an apparatus 400 for decoding a picture 12′ accordingto an embodiment of the present disclosure. For example the apparatus400 may be similar to the decoder 20. The apparatus 400 is configured topartition the picture 12′ into coding blocks 425 using recursivemulti-tree splitting depending on the splitting information 415 signaledin the data stream 14. The apparatus 400 is further configured to decodethe picture 12′ from coding information 440 which is signaled in thedata stream 14. The coding information 416 relates to the coding blocks425. For partitioning the picture 12′ into the coding blocks 425, theapparatus 400 is configured for decoding a split flag 416 of thesplitting information 415 from the data stream 14. The split flag 416indicates whether a predetermined block 411 of the picture 12′ is to besplit or not to be split, thereby stopping the recursive multi-treesplitting with the predetermined block 411 becoming one of the codingblocks 425. If the split flag 416 indicates that the predetermined block411 of the picture 12′ is to be split, the apparatus 400 is configuredfor decoding a quad flag 417 of the splitting information 415 from thedata stream 14 which indicates whether the predetermined block 411 ofthe picture 12′ is to be split into four child blocks 412 or not.

If the split flag 416 indicates that the predetermined block of thepicture 12′ is to be split, and if the quad flag 417 indicates that thepredetermined block 411 of the picture 12′ is not to be split into fourchild blocks 412, the partitioning of the picture 12′ comprises decodingone or more further flags 418 of the splitting information 415 from thedata stream 14 which indicate whether the predetermined block 411 of thepicture 12′ is to be split into two or three child blocks 412 verticallyor horizontally.

Further, if the split flag 416 indicates that the predetermined block411 of the picture 12′ is to be split, the partitioning of the picture12′ comprises resuming the recursive multi-tree splitting for the childblocks 412 using even further flags of the splitting information 415.For example, in a further recursion of the recursive multi-treesplitting, one of the child blocks 412 may be the predetermined block411.

For example, the apparatus 400 may be configured to receive the datastream 14, the data stream 14 comprising the splitting information 415and the coding information 440. The apparatus 400 may further beconfigured to decode the picture 12′ from the data stream to provide adecoded signal comprising the picture 12′. For example, thepredetermined block 411 may be any block of the picture 12′, which issubject to a current recursion of the recursive multi-tree splitting,that is, a block for which the current recursion may infer a splitting.For example the predetermined block 411 of a first recursion of therecursive multi-tree splitting may be a tree root block, such as a CTU.If the split flag 416 indicates that the predetermined block 411 of thepicture 12′ is to be split, the apparatus 400 is configured for resumingthe recursive multi-tree splitting for the child blocks of thepredetermined blocks 411. The child blocks 412 may be the one or moresub-blocks of the predetermined block 411 resulting from partitioningthe predetermined block. For example, the apparatus 400 is configured toresume the recursive multi-tree splitting by selecting one of the childblocks 412 of the predetermined block as the predetermined block 411 fora subsequent recursion of the partitioning and performing thepartitioning as described for the predetermined block. For example, ifthe split flag 416 indicates that the predetermined block 411 of thepicture 12′ is not to be split, the apparatus 400 may be configured tostop the recursive multi-tree splitting with the predetermined block 411becoming one of the coding blocks 425. The apparatus 400 may thancontinue the partitioning with another block, e.g. a sister block of thepredetermined block or a sister block of a parent block of thepredetermined block or another block.

Thus, according to an embodiment, the apparatus 400 is configured toresume the recursive multi-tree splitting for the child blocks 412 usingeven further flags of the splitting information 415 by, for apredetermined child block of the child blocks 412, decoding a furthersplit flag 416 of the splitting information 415 from the data stream 14which indicates whether the predetermined child block of the picture 12′is to be split or not to be split thereby stopping the recursivemulti-tree splitting with the predetermined child block becoming acoding block. If the further split flag 416 indicates that thepredetermined child block of the picture 12′ is to be split, resumingthe recursive multi-tree splitting for the child blocks 412 comprisesdecoding a further quad flag 417 of the splitting information 415 fromthe data stream 14 which indicates whether the predetermined child blockof the picture 12′ is to be split into four child blocks 412 or not. Ifthe further split flag 416 indicates that the predetermined child blockof the picture 12′ is to be split, and if the further quad flag 417indicates that the predetermined child block of the picture 12′ is notto be split into four child blocks 412, resuming the recursivemulti-tree splitting for the child blocks 412 comprises decoding one ormore further flags 418 of the splitting information 415 from the datastream 14 which indicate whether the predetermined child block of thepicture 12′ is to be split into two or three child blocks 412 verticallyor horizontally. Further, if the further split flag 416 indicates thatthe predetermined child block of the picture 12′ is to be split,resuming the recursive multi-tree splitting for the child blocks 412comprises resuming the recursive multi-tree splitting for the childblocks 412 of the predetermined child block using even further flags ofthe splitting information 415.

That is, for example, the apparatus 400 is configured to resume therecursive multi-tree splitting for the child blocks 412 by selecting oneof the child blocks 425 that resulted from splitting the predeterminedblock 411 in a recursion of the recursive multi-tree splitting for asubsequent recursion of the recursive multi-tree splitting. For example,the recursive splitting may be stopped if the split flag 416 referringto the predetermined block 411 of the current recursion, e.g. thepredetermined block or the predetermined child block, indicates that thepredetermined block 411 is not to be split.

For example, in FIGS. 10A and 10B, the splitting of the node A into thefour nodes B, C, D, E as shown in FIGS. 10A and 10B may represent asplitting of the predetermined block 411 into the child blocks 412, asmay be a possible result of one recursion of the recursive multi-treesplitting as described with respect to the apparatus 400 and theapparatuses described with respect to subsequent figures.

FIG. 12 illustrates an alternative partitioning tree 1200 separating thesplit and the type information, e.g. an information about a type of thesplit. For example, the partitioning tree 1200 may represent onerecursion of the recursive splitting according to an exemplaryembodiment of the apparatus 400.

A property of the partitioning tree 1100 of FIG. 11 is that the “nofurther split” option involves the transmission of two syntax elements,e.g. it may involve indicating to not perform a quadtree split in afirst syntax element and to indicate to not further split the parentblock 1111 using a second syntax element. Since the split informationcan be represented interpedently of the shape type after the splitinformation, an exemplary embodiment of the presented invention modifiesthe partitioning tree as shown in FIG. 12. Note that the syntax remainsthe same relative to the partitioning tree 1100 denoted in FIG. 11 whenthe second depth has been reached, i.e., when the mtt_vertical_flag istransmitted. Thus, the modification to the syntax elementsmtt_vertical_flag and mtt_split_binary_flag is applicable to thebinarization schemes depicted in both FIG. 11 and FIG. 12. For example,partitioning schemes of embodiments of the present invention may besimilar to the partitioning tree 1100 of FIG. 1100, but may use amodified syntax for defining the splitting type. By separating the splitand the type information, the cost for the no split option can bereduced, which can become important at lower bit rates operation points.

In other words, embodiments of the presented invention describe ageneric concept that further improves the compression efficiency byinvolving adaptive tree structures and an associated context modeling.

For example, the partitioning trees illustrated in FIGS. 11 and 12 mayonly depict a common case where all options are possible. However, eachnode may inherit availability constraints. Examples for such constraintsare size constraints, (e.g., no split is allowed that would results inchild nodes having dimensions smaller than the minimal allowed blocksize), consecutive split restrictions (e.g., a quadtree split might onlybe signaled if the previous split was also a quadtree split). For thesereasons, each of the syntax elements within the partitioning tree mayslightly change their meaning depending on the particular availabilityconstraints. That is, for example, some or all options for splitting maynot be available for the predetermined block 411.

Embodiments of the invention may explicitly use the availabilityinformation, e.g. information about the available options for splittingthe predetermined block 411, for the context modeling for the syntaxelements of the partitioning tree. The availability information enrichesthe context modeling so that additional options, e.g. for the contextmodelling, are possible. For example, an information indicated by apredetermined flag of the splitting information 415 may be inferred byusing the context model, so that said information may be inferredwithout decoding the predetermined flag. Thus, the splitting information415 does not necessarily need to comprise the predetermined flag, sothat the size of the data stream 14 may be reduced. For example, thecontext modelling may depend on one or more criteria.

In general, embodiments of the present invention may employ variousimplementations of partitioning trees for recursively splitting apicture. The partitioning may rely on a number of flags, each of whichmay indicate whether a splitting option, the respective flag refers to,is to be applied to a predetermined block which is subject to a currentrecursion of the recursive splitting. The flags may be part of asplitting information, which may be contained in a data stream. However,flags may also be inferred from said availability information. Further,for decoding the flags, from the data stream, or from the splittinginformation, context modelling may be used. For example, contextmodelling may use available information for reducing a number ofpossible options, so that one or more flags may be encoded to or decodedfrom less information, reducing a size of the data stream. For example,the partitioning of a picture may rely on one or more of the split flag416, the quad flag 417, a split direction flag 518 and a triple flag519. An exemplary order for evaluating such flags is shown in FIG. 12.Each of the embodiments described with respect to FIGS. 4-9 and 13-18may employ different orders or dependencies or conditions for evaluatingor decoding one or more of said flags. For example, different types forcontext modelling may be employed. Context modelling may, for examplerely on the described availability information, or rely on informationabout neighboring blocks, e.g. block that have already been partitioned.

For example, a first context may be used for decoding the split flag416, however different embodiments may employ different criteria orassumptions or information for deriving the first context.

For example, a second context may be used for decoding the splitdirection flag 418, however different embodiments may employ differentcriteria or assumptions or information for deriving the second context.

For example, a third context may be used for decoding the triple flag419, however different embodiments may employ different criteria orassumptions or information for deriving the third context.

In other words, the context modeling for some or all syntax elements ofthe partitioning tree may depend only on the availability information.Second, the context modeling for some or all syntax elements of thepartitioning tree may be a mix of the availability information with someother information, e.g the partitioning structure information of theneighboring blocks (tree depth or size).

According to an embodiment, the apparatus 400 is configured to infer,depending on one or more criteria being fulfilled or not, that one ormore flags of the splitting information 415 assume a predetermined flagstate with not decoding the one or more flags of the splittinginformation 415 from the data stream 14.

For example, the data stream 14 does not necessarily comprise all or anyof the split flag 416, the quad flag 417 and the further flags 418 forthe predetermined block. For example, the apparatus 400 may beconfigured to infer a flag state of one or more or all of said flags forthe predetermined block, for example from information about thepredetermined block 411 or about neighboring blocks.

According to an embodiment, the one or more criteria relate to one ormore of child block area, child block width, child block height, acurrent split depth and a split line alignment with a picture border.For example, there may be a lower limit for the area, the width, or theheight of the child blocks 425 that result from a splitting of thepredetermined block 411. The apparatus 400 may predict said measures forthe child blocks 425, from which the apparatus 400 may infer that theone or more flags of the splitting information 415, e.g. the split flag416, the quad flag 417 or the one or more further flags 418, assume apredetermined flag state. For example, the apparatus 400 may infer fromthe said measures, that the predetermined block 411 is not to be splitfurther, or that the predetermined block 411 is not to be split intofour child blocks 412. For example, the current split depth may refer toa tree depth or a quad-tree depth, that is, for example, a number ofrecursions of the recursive splitting that were performed to obtain thepredetermined block 411.

According to an embodiment, the apparatus 400 is configured to start therecursive multi-tree splitting at each tree-root block of tree-rootblocks into which the picture 12′ is subdivided in rows and columns.

According to an embodiment, the apparatus 400 is configured to start therecursive multi-tree splitting at tree-root blocks into which thepicture 12′ is subdivided in rows and columns.

According to an embodiment, the apparatus 400 is configured to inferthat the quad flag 417 indicates that the predetermined block 411 of thepicture 12′ is not to be split into four child blocks 412 and suppressthe decoding of the quad flag 417 from the data stream 14, if a firstpredetermined criterion is fulfilled.

According to an embodiment, the apparatus 400 is configured so that thefirst predetermined criterion is fulfilled if the predetermined block411 results from a non-quad split of a parent block.

According to an embodiment, the apparatus 400 is configured to, in thedecoding of the one or more further flags 418, decode a split directionflag from the data stream 14 which indicates whether the predeterminedblock 411 of the picture 12′ is to be split vertically or horizontally.Further, for decoding the one or more further flags 418, the apparatus400 may be configured to decode a triple flag from the data stream 14which indicates whether the predetermined block 411 of the picture 12′is to be split into three child blocks 412 or into two child blocks 412.

According to an embodiment, the apparatus 400 is configured to inferthat the split direction flag indicates that the predetermined block 411of the picture 12′ is to be split vertically and suppress the decodingof the split direction flag from the data stream 14, if a secondpredetermined criterion is fulfilled, and infer that the split directionflag indicates that the predetermined block 411 of the picture 12′ is tobe split horizontally and suppress the decoding of the split directionflag from the data stream 14, if a third predetermined criterion isfulfilled.

According to an embodiment, the second predetermined criterion isfulfilled if halving the predetermined block 411 horizontally wouldyield a width falling below a predetermined minimum dimension, and thethird predetermined criterion is fulfilled if halving the predeterminedblock 411 vertically would yield a height falling below thepredetermined minimum dimension.

According to an embodiment, the apparatus 400 is configured to inferthat the triple flag indicates that the predetermined block 411 of thepicture 12′ is to be split into two child blocks 412 and suppress thedecoding of the triple flag from the data stream 14, if a fourthpredetermined criterion is fulfilled.

According to an embodiment, the apparatus 400 is configured to inferthat the triple flag indicates that the predetermined block 411 of thepicture 12′ is to be split into two child blocks 412 and suppress thedecoding of the triple flag from the data stream 14, if a fourthpredetermined criterion is fulfilled, and the apparatus 400 is furtherconfigured to infer that the triple flag indicates that thepredetermined block 411 of the picture 12′ is to be split into threechild blocks 412 and suppress the decoding of the triple flag from thedata stream 14, if a fifth predetermined criterion is fulfilled.

According to an embodiment, the fourth predetermined criterion isfulfilled if trisecting the predetermined block 411 in a split directionindicated by the direction flag would yield a dimension of thepredetermined block 411 along the split direction which split fallsbelow a predetermined minimum dimension.

According to an embodiment, the fifth predetermined criterion isfulfilled if halving the predetermined block 411 in a split directionindicated by the direction flag would yield a dimension of thepredetermined block 411 along the split direction which exceeds apredetermined maximum dimension.

According to an embodiment, the apparatus 400 is configured to resumethe recursive multi-tree splitting for the child blocks 412 using evenfurther flags of the splitting information 415 by, for a predeterminedchild block of the child blocks 412, decoding a further quad flag 417 ofthe splitting information 415 from the data stream 14 which indicateswhether the predetermined child block of the picture 12′ is to be splitinto four child blocks 412 or not. If the further quad flag 417indicates that the predetermined child block of the picture 12′ is notto be split into four child blocks 412, resuming the recursivemulti-tree splitting for the predetermined child block comprisesdecoding a further split flag 416 of the splitting information 415 fromthe data stream 14 which indicates whether the predetermined child blockof the picture 12′ is to be split, or not to be split thereby stoppingthe recursive multi-tree splitting with the predetermined child blockbecoming a coding block. If the further quad flag 417 indicates that thepredetermined child block of the picture 12′ is not to be split intofour child blocks 412, and if the further split flag 416 indicates thatthe predetermined child block of the picture 12′ is to be split,resuming the recursive multi-tree splitting for the predetermined childblock comprises decoding one or more further flags 418 of the splittinginformation 415 from the data stream 14 which indicate whether thepredetermined child block of the picture 12′ is to be split into two orthree child blocks 412 vertically or horizontally. If the further quadflag 417 indicates that the predetermined child block of the picture 12′is not to be split into four child blocks 412, or if the further splitflag 416 indicates that the predetermined child block of the picture 12′is to be split, resuming the recursive multi-tree splitting for thepredetermined child block comprises resuming the recursive multi-treesplitting for the child blocks 412 of the predetermined child blockusing even further flags of the splitting information 415. That is, forexample, an order of the split flag 416 and the quad flag 417 may bedifferent for different recursions of the recursive splitting.

According to an embodiment, the apparatus 400 is configured to inferthat the quad flag 417 indicates that the predetermined block 411 of thepicture 12′ is not to be split into four child blocks 412 and suppressthe decoding of the quad flag 417 from the data stream 14, if a firstpredetermined criterion is fulfilled. According to this embodiment, theapparatus 400 is further configured to decode the split flag 416 of thesplitting information 415 from the data stream 14 by context adaptiveentropy decoding using a first context which depends on whether thefirst predetermined criterion is fulfilled.

For example, in the binarization presented in FIG. 12, split_flag, e.g.the split flag 416, might be modelled as shown in Table 1 (c.f. FIG.19), conditioned on the following information:

-   -   Availability of the quadtree split (QT)    -   The current quadtree depth    -   The current width and height    -   The current luma area    -   The width of the above neighbor    -   The height of the left neighbors.

Table 1, shown in FIG. 19, shows an exemplarily context modeling for thesyntax element split_flag, e.g. the split flag 416, using availabilityinformation and existing context modeling. The context modeling isconditioned to the availability of the quadtree split (QT), the currentquadtree depth, the current width and height, the current luma area(W×H), and the width of the above neighbor and height of the leftneighbor.

According to an embodiment, the first context additionally depends on anumber of splits of the recursive multi-tree splitting using which thepredetermined block 411 is obtained. For example, such a dependence maybe modeled as shown in the second column of Tab. 1. Alternatively oradditionally, the first context additionally depends on a size of thepredetermined block 411. For example, such a dependence may be modeledas shown in the third column of Tab. 1.

According to an embodiment, the first context additionally depends onwhether, and discriminates between, a number of splits of the recursivemulti-tree splitting using which the predetermined block 411 isobtained, is below a predetermined threshold number of splits.Alternatively, the first context additionally depends on [whether], anddiscriminates between, whether a size of the predetermined block 411 isabove a predetermined threshold size.

According to an embodiment, the first context additionally depends on awidth of a coding block above the predetermined block 411, and a heightof a coding block to the left of the predetermined block 411. An exampleof such a dependence of a context model is shown in the fourth and fifthcolumn of Tab. 1.

According to an embodiment, the first context additionally depends onwhether, and discriminates between:

-   -   a width of a coding block above the predetermined block 411 is        smaller than a width of the predetermined block 411 and a height        of a coding block to the left of the predetermined block 411 is        smaller than a height of the predetermined block 411    -   the width of the coding block above the predetermined block 411        is smaller than the width of the predetermined block 411 and the        height of the coding block to the left of the predetermined        block 411 is larger than the height of the predetermined block        411    -   the width of the coding block above the predetermined block 411        is smaller than the width of the predetermined block 411 and the        height of the coding block to the left of the predetermined        block 411 is larger than the height of the predetermined block        411 or the width of the coding block above the predetermined        block 411 is larger than the width of the predetermined block        411 and the height of the coding block to the left of the        predetermined block 411 is smaller than the height of the        predetermined block 411

For example, such a dependence of a context model is represented in bythe context modelling shown in Tab. 1 in FIG. 19.

According to an embodiment, the apparatus 400 is configured to performthe splitting into four child blocks 412 so that the four child blocks412 are equally sized and arranged in a 2×2 array. According to thisembodiment, the apparatus 400 is configured to perform the recursivemulti-tree splitting using a depth first traversal order and traversechild blocks resulting from splitting one parent block from left toright in case of a horizontal split, from top to bottom in case of avertical split and in a row-wise raster scan order from top left tobottom right in case of a splitting into four child blocks 412.

According to an embodiment, for the decoding of one or more furtherflags 418 of the splitting information 415 from the data stream 14 whichindicate whether the predetermined child block of the picture 12′ is tobe split into two or three child blocks 412 vertically or horizontally,the apparatus 400 is configured to decode a split direction flag fromthe data stream 14 which indicates whether the predetermined block 411of the picture 12′ is to be split vertically or horizontally, andfurther, to decode a triple flag from the data stream 14 which indicateswhether the predetermined block 411 of the picture 12′ is to be splitinto three child blocks 412 or into two child blocks 412. Further, if afirst predetermined criterion is fulfilled, the apparatus 400 isconfigured to infer that the quad flag 417 indicates that thepredetermined block 411 of the picture 12′ is not to be split into fourchild blocks 412 and to suppress the decoding of the quad flag 417 fromthe data stream 14. If a second predetermined criterion is fulfilled,the apparatus is configured to infer that the split direction flagindicates that the predetermined block 411 of the picture 12′ is to besplit vertically and suppress the decoding of the split direction flagfrom the data stream 14. If a third predetermined criterion isfulfilled, the apparatus 400 is configured to infer that the splitdirection flag indicates that the predetermined block 411 of the picture12′ is to be split horizontally and configured to suppress the decodingof the split direction flag from the data stream 14. If a fourthpredetermined criterion is fulfilled, the apparatus 400 is configured toinfer that the triple flag indicates that the predetermined block 411 ofthe picture 12′ is to be split into two child blocks 412 and suppressthe decoding of the triple flag from the data stream 14. Further, theapparatus is configured to decode the split flag 416 of the splittinginformation 415 from the data stream 14 by context adaptive entropydecoding using a first context which depends on a sum of addends each ofwhich is associated with, and assumes a non-zero value if, while beingzero otherwise, one of the following scenarios is fulfilled:

-   -   the first predetermined criterion is not fulfilled,    -   the second predetermined criterion is not fulfilled,    -   the third predetermined criterion is not fulfilled,    -   the second predetermined criterion is not fulfilled and the        fourth predetermined criterion would not be fulfilled in case of        a split direction indicated by the split direction flag being        horizontal,    -   the third predetermined criterion is not fulfilled and the        fourth predetermined criterion would not be fulfilled in case of        the split direction indicated by the split direction flag being        vertical, respectively.

For example, here, if is implied that Tx implies Bx; the concordancewith above description is described using following Boolean logic rulesbelow:

-   Frist predetermined criterion: not not QT, i.e. QT-   Second predetermined criterion: not ((not BH) and (not TH)), i.e. BH    or TH-   Third predetermined criterion: not ((not BV) and (not TV)), i.e. BV    or TV-   Fourth predetermined criterion: (not ((not BH) and (not TH))) and    (not (not TH)), i.e. (BH or TH) and TH, i.e. TH-   Fifth predetermined criterion: (not ((not BV) and (not TV))) and    (not (not TV)), i.e. (BV or TV) and TV, i.e. TV.

According to an embodiment, the apparatus 400 is configured to, in thedecoding of one or more further flags 418 of the splitting information415 from the data stream 14 which indicate whether the predeterminedchild block of the picture 12′ is to be split into two or three childblocks 412 vertically or horizontally, decode a split direction flagfrom the data stream 14 which indicates whether the predetermined block411 of the picture 12′ is to be split vertically or horizontally, and todecode a triple flag from the data stream 14 which indicates whether thepredetermined block 411 of the picture 12′ is to be split into threechild blocks 412 or into two child blocks 412. The apparatus 400 isfurther configured to infer that the quad flag 417 indicates that thepredetermined block 411 of the picture 12′ is not to be split into fourchild blocks 412 and configured to suppress the decoding of the quadflag 417 from the data stream 14, if a first predetermined criterion isfulfilled. The apparatus 400 is further configured to infer that thesplit direction flag indicates that the predetermined block 411 of thepicture 12′ is to be split vertically and suppress the decoding of thesplit direction flag from the data stream 14, if a second predeterminedcriterion is fulfilled. The apparatus 400 is further configured to inferthat the split direction flag indicates that the predetermined block 411of the picture 12′ is to be split horizontally and suppress the decodingof the split direction flag from the data stream 14, if a thirdpredetermined criterion is fulfilled. The apparatus 400 is furtherconfigured to infer that the triple flag indicates that thepredetermined block 411 of the picture 12′ is to be split into two childblocks 412 and suppress the decoding of the triple flag from the datastream 14, if a fourth predetermined criterion is fulfilled, and toinfer that the triple flag indicates that the predetermined block 411 ofthe picture 12′ is to be split into three child blocks 412 and suppressthe decoding of the triple flag from the data stream 14, if a fifthpredetermined criterion is fulfilled. The apparatus 400 is furtherconfigured to decode the split flag 416 of the splitting information 415from the data stream 14 by context adaptive entropy decoding using afirst context which depends on a sum of addends each of which isassociated with one of the following scenarios. Each of the addendsassumes a non-zero value if, while being zero otherwise, the respectivescenario is fulfilled:

-   -   the first predetermined criterion is not fulfilled    -   the second predetermined criterion is not fulfilled, and the        fifth predetermined criterion would not be fulfilled in case of        the split direction indicated by the split direction flag being        horizontal    -   the third predetermined criterion is not fulfilled, and the        fifth predetermined criterion would not be fulfilled in case of        the split direction indicated by the split direction flag being        vertical    -   the second predetermined criterion is not fulfilled and the        fourth predetermined criterion would not be fulfilled in case of        the split direction indicated by the split direction flag being        horizontal    -   the third predetermined criterion is not fulfilled and the        fourth predetermined criterion would not be fulfilled in case of        the split direction indicated by the split direction flag being        vertical, respectively.

According to an embodiment, the first context additionally depends onwhether, and discriminates between, a third of the sum of addends plusone is zero, one and two. According to this embodiment, the non-zerovalue of the addend associated with the first predetermined criterionbeing not fulfilled is two, and the non-zero values of the other addendsare one.

According to an embodiment, the first context additionally depends on awidth of a coding block above the predetermined block 411, and a heightof a coding block to the left of the predetermined block 411.

According to an embodiment, the first context additionally depends onwhether, and discriminates between:

-   -   a width of a coding block above the predetermined block 411 is        smaller than a width of the predetermined block 411 and a height        of a coding block to the left of the predetermined block 411 is        smaller than a height of the predetermined block 411    -   the width of the coding block above the predetermined block 411        is smaller than the width of the predetermined block 411 and the        height of the coding block to the left of the predetermined        block 411 is larger than the height of the predetermined block        411    -   the width of the coding block above the predetermined block 411        is smaller than the width of the predetermined block 411 and the        height of the coding block to the left of the predetermined        block 411 is larger than the height of the predetermined block        411 or the width of the coding block above the predetermined        block 411 is larger than the width of the predetermined block        411 and the height of the coding block to the left of the        predetermined block 411 is smaller than the height of the        predetermined block 411

In other words, the modelling of the split_flag, e.g. the first contextfor decoding the split flag 416, might depend on the number of availablesplits N_(s), defined as follows: N_(s)=(2·QT+BH+BV+TH+TV−1), where QT,BH, BV, TH and TV represent the availability of the quad split, binaryhorizontal, binary vertical, ternary horizontal and ternary verticalsplits. The alternative context modeling, e.g. for the first context fordecoding the split flag 416, may thus depends on the following:

-   -   Number of available splits N_(s)    -   The current width and height    -   The width of the above neighbor    -   The height of the left neighbors

Table 2, shown in FIG. 20, shows this alternative context modeling forthe syntax element split_flag, e.g. the split flag 416, depending on theavailability of all the splits, as well as the sizes of neighboringblocks.

According to an embodiment, the apparatus 400 is configured to, in thedecoding of the one or more further flags 418 of the splittinginformation 415 from the data stream 14 which indicate whether thepredetermined child block of the picture 12′ is to be split into two orthree child blocks 412 vertically or horizontally, decode a splitdirection flag from the data stream 14 which indicates whether thepredetermined block 411 of the picture 12′ is to be split vertically orhorizontally, if neither a second nor a third predetermined criterion isfulfilled. If the second predetermined criterion is fulfilled, thedecoding of the one or more further flags 418 comprises inferring thatthe split direction flag indicates that the predetermined block 411 ofthe picture 12′ is to be split vertically. If the third predeterminedcriterion is fulfilled, the decoding of the one or more further flags418 comprises inferring that the split direction flag indicates that thepredetermined block 411 of the picture 12′ is to be split horizontally.If a fourth predetermined criterion is not fulfilled, the decoding ofthe one or more further flags 418 comprises decoding a triple flag fromthe data stream 14 which indicates whether the predetermined block 411of the picture 12′ is to be split into three child blocks 412 or intotwo child blocks 412. If the fourth predetermined criterion isfulfilled, the decoding of the one or more further flags 418 comprisesinferring that the triple flag indicates that the predetermined block411 of the picture 12′ is to be split into two child blocks 412.Further, the apparatus 400 is configured to decode the split directionflag from the data stream 14 by context adaptive entropy decoding usinga second context which depends on whether, and discriminates between:

-   -   the fourth predetermined criterion would not neither be        fulfilled in case of a split direction indicated by the split        direction flag being horizontal nor in case of the split        direction indicated by the split direction flag being vertical        or be fulfilled both in case of a split direction indicated by        the split direction flag being horizontal as well as in case of        the split direction indicated by the split direction flag being        vertical    -   the fourth predetermined criterion would be fulfilled in case of        the split direction indicated by the split direction flag being        horizontal and not be fulfilled in case of the split direction        indicated by the split direction flag being vertical    -   the fourth predetermined criterion would not be fulfilled in        case of the split direction indicated by the split direction        flag being horizontal and be fulfilled in case of the split        direction indicated by the split direction flag being vertical

According to an embodiment, the apparatus 400 is configured to, in thedecoding of one or more further flags 418 of the splitting information415 from the data stream 14 which indicate whether the predeterminedchild block of the picture 12′ is to be split into two or three childblocks 412 vertically or horizontally, decode a split direction flagfrom the data stream 14 which indicates whether the predetermined block411 of the picture 12′ is to be split vertically or horizontally, ifneither a second nor a third predetermined criterion is fulfilled. Ifthe second predetermined criterion is fulfilled, the decoding of the oneor more further flags 418 comprises inferring that the split directionflag indicates that the predetermined block 411 of the picture 12′ is tobe split vertically. If the third predetermined criterion is fulfilled,the decoding of the one or more further flags 418 comprises inferringthat the split direction flag indicates that the predetermined block 411of the picture 12′ is to be split horizontally. If fourth and fifthpredetermined criteria are not fulfilled, the decoding of the one ormore further flags 418 comprises decoding a triple flag from the datastream 14 which indicates whether the predetermined block 411 of thepicture 12′ is to be split into three child blocks 412 or into two childblocks 412. If the fourth predetermined criterion is fulfilled, thedecoding of the one or more further flags 418 comprises inferring thatthe triple flag indicates that the predetermined block 411 of thepicture 12′ is to be split into two child blocks 412 and to suppress thedecoding of the triple flag from the data stream 14. If the fifthpredetermined criterion is fulfilled, the decoding of the one or morefurther flags 418 comprises inferring that the triple flag indicatesthat the predetermined block 411 of the picture 12′ is to be split intothree child blocks 412 and to suppress the decoding of the triple flagfrom the data stream 14. Further, the apparatus 400 is configure todecode the split direction flag from the data stream 14 by contextadaptive entropy decoding using a second context which depends onwhether, and discriminates between:

-   -   a first number of criteria among the fourth and fifth        predetermined criteria which would be fulfilled in case of a        split direction indicated by the split direction flag being        horizontal equals a second number of criteria among the fourth        and fifth predetermined criteria which would be fulfilled in        case of the split direction indicated by the split direction        flag being vertical    -   the first number being greater than the second number    -   the first number being smaller than the second number

FIG. 5 illustrates an apparatus 500 for decoding a picture 12′ accordingto an embodiment of the present disclosure. For example the apparatus500 may be similar to the decoder 20. The apparatus 500 is configured topartition the picture 12′ into coding blocks 425 using recursivemulti-tree splitting depending on splitting information 415 signaled ina data stream 14. Further, the apparatus 500 is configured to decode thepicture 12′ from coding information 440 which is signaled in the datastream 14 and relates to the coding blocks 425. The apparatus 500 isconfigured to partition the picture 12′ into the coding blocks 425depending on splitting information 415 signaled in a data stream 14 bydecoding a split flag 416 and a quad flag 417 of the splittinginformation 415 from the data stream 14, wherein the split flag 416indicates whether a predetermined block 411 of the picture 12′ is to besplit or not to be split thereby stopping the recursive multi-treesplitting with the predetermined block 411 becoming one of the codingblocks 425. The quad flag 417 indicates whether the predetermined block411 of the picture 12′ is to be split into four child blocks 412 or not.If the predetermined block 411 of the picture 12′ is to be split, butnot to be split into four child blocks 412, and if neither a second nora third predetermined criterion is fulfilled, the partitioning of thepicture 12′ comprises decoding a split direction flag 518 from the datastream 14 which indicates whether the predetermined block 411 of thepicture 12′ is to be split vertically or horizontally. If thepredetermined block 411 of the picture 12′ is to be split, but not to besplit into four child blocks 412, and if the second predeterminedcriterion is fulfilled, the partitioning of the picture 12′ comprisesinferring that the split direction flag 518 indicates that thepredetermined block 411 of the picture 12′ is to be split vertically. Ifthe predetermined block 411 of the picture 12′ is to be split, but notto be split into four child blocks 412, and if the third predeterminedcriterion is fulfilled, the partitioning of the picture 12′ comprisesinferring that the split direction flag 518 indicates that thepredetermined block 411 of the picture 12′ is to be split horizontally.If the predetermined block 411 of the picture 12′ is to be split, butnot to be split into four child blocks 412, and if a fourthpredetermined criterion is not fulfilled, the partitioning of thepicture 12′ comprises decoding a triple flag 519 from the data stream 14which indicates whether the predetermined block 411 of the picture 12′is to be split into three child blocks 412 or into two child blocks 412.If the predetermined block 411 of the picture 12′ is to be split, butnot to be split into four child blocks 412, and if the fourthpredetermined criterion is fulfilled, the partitioning of the picture12′ comprises inferring that the triple flag 519 indicates that thepredetermined block 411 of the picture 12′ is to be split into two childblocks 412. If the predetermined block 411 of the picture 12′ is to besplit, the partitioning of the picture 12′ comprises resuming therecursive multi-tree splitting for the child blocks 412 using evenfurther flags of the splitting information 415. Further, the apparatus500 is configured to decode the split direction flag 518 from the datastream 14 by context adaptive entropy decoding using a second context552 which depends on whether, and discriminates between:

-   -   the fourth predetermined criterion would not neither be        fulfilled in case of a split direction indicated by the split        direction flag 518 being horizontal nor in case of the split        direction indicated by the split direction flag 518 being        vertical or be fulfilled both in case of a split direction        indicated by the split direction flag 518 being horizontal as        well as in case of the split direction indicated by the split        direction flag 518 being vertical    -   the fourth predetermined criterion would be fulfilled in case of        the split direction indicated by the split direction flag 518        being horizontal and not be fulfilled in case of the split        direction indicated by the split direction flag 518 being        vertical    -   the fourth predetermined criterion would not be fulfilled in        case of the split direction indicated by the split direction        flag 518 being horizontal and be fulfilled in case of the split        direction indicated by the split direction flag 518 being        vertical

FIG. 6 illustrates an apparatus 600 for decoding a picture 12′ accordingto an embodiment of the present disclosure. For example the apparatus500 may be similar to the decoder 20. Compared to the apparatus 600, theapparatus 500 may additionally use a fifth criterion for inferring apredetermined state of the triple flag 519, and the second context usedfor decoding the split direction flag 518 may be different.

The apparatus 600 is configured to partition the picture 12′ into codingblocks 425 using recursive multi-tree splitting depending on splittinginformation 415 signaled in a data stream 14, and further, to decode thepicture 12′ from coding information 440 which is signaled in the datastream 14 and relates to the coding blocks 425. The apparatus 600 isconfigured to partition the picture 12′ into the coding blocks 425depending on splitting information 415 signaled in a data stream 14 bydecoding a split flag 416 and a quad flag 417 of the splittinginformation 415 from the data stream 14, wherein the split flag 416indicates whether a predetermined block 411 of the picture 12′ is to besplit or not to be split thereby stopping the recursive multi-treesplitting with the predetermined block 411 becoming one of the codingblocks 425. The quad flag 417 indicates whether the predetermined block411 of the picture 12′ is to be split into four child blocks 412 or not.If the predetermined block 411 of the picture 12′ is to be split, butnot to be split into four child blocks 412, and if neither a second nora third predetermined criterion is fulfilled, the partitioning of thepicture 12′ comprises decoding a split direction flag 518 from the datastream 14 which indicates whether the predetermined block 411 of thepicture 12′ is to be split vertically or horizontally. If thepredetermined block 411 of the picture 12′ is to be split, but not to besplit into four child blocks 412, and if the second predeterminedcriterion is fulfilled, the partitioning of the picture 12′ comprisesinferring that the split direction flag 518 indicates that thepredetermined block 411 of the picture 12′ is to be split vertically. Ifthe predetermined block 411 of the picture 12′ is to be split, but notto be split into four child blocks 412, and if the third predeterminedcriterion is fulfilled, the partitioning of the picture 12′ comprisesinferring that the split direction flag 518 indicates that thepredetermined block 411 of the picture 12′ is to be split horizontally.If the predetermined block 411 of the picture 12′ is to be split, butnot to be split into four child blocks 412, and if a fourthpredetermined criterion is not fulfilled, the partitioning of thepicture 12′ comprises decoding a triple flag 519 from the data stream 14which indicates whether the predetermined block 411 of the picture 12′is to be split into three child blocks 412 or into two child blocks 412.If the predetermined block 411 of the picture 12′ is to be split, butnot to be split into four child blocks 412, and if the thirdpredetermined criterion is fulfilled, the partitioning of the picture12′ comprises inferring that the triple flag 519 indicates that thepredetermined block 411 of the picture 12′ is to be split into two childblocks 412, if the fourth predetermined criterion is fulfilled, and thatthe triple flag 519 indicates that the predetermined block 411 of thepicture 12′ is to be split into three child blocks 412 and suppress thedecoding of the triple flag 519 from the data stream 14, if a fifthpredetermined criterion is fulfilled. If the predetermined block 411 ofthe picture 12′ is to be split, the partitioning of the picture 12′comprises resuming the recursive multi-tree splitting for the childblocks 412 using even further flags of the splitting information 415.The apparatus 600 is further configured to decode the split directionflag 518 from the data stream 14 by context adaptive entropy decodingusing a second context 552. According to this embodiment, the secondcontext 552 depends on whether, and discriminates between, a scenario ofthe following and which of the following scenarios being fulfilled. Anexemplary illustration of the scenarios for the second context 552 isshown in FIG. 7.

-   -   a first number of criteria among the fourth and fifth        predetermined criteria which would be fulfilled in case of a        split direction indicated by the split direction flag 518 being        horizontal equals a second number of criteria among the fourth        and fifth predetermined criteria which would be fulfilled in        case of the split direction indicated by the split direction        flag 518 being vertical. This case may be represented by        scenario 791 in FIG. 7.    -   the first number being greater than the second number. This case        may be represented by scenario 792 in FIG. 7.    -   the first number being smaller than the second number. This case        may be represented by scenario 793 in FIG. 7.

According to an embodiment, the second context 552 additionally dependson whether, and discriminates between,

-   -   a width of the predetermined block 411 equaling a height of the        current block    -   the width of the predetermined block 411 being larger than the        height of the current block    -   the width of the predetermined block 411 being smaller than the        height of the current block

According to an embodiment, if the fourth predetermined criterion wouldnot neither be fulfilled in case of a split direction indicated by thesplit direction flag 518 being horizontal nor in case of the splitdirection indicated by the split direction flag 518 being vertical or befulfilled both in case of a split direction indicated by the splitdirection flag 518 being horizontal as well as in case of the splitdirection indicated by the split direction flag 518 being vertical, thesecond context 552, additionally depends on whether, and discriminatesbetween,

-   -   a width of the predetermined block 411 equaling a height of the        current block, e.g. a height of the predetermined block 411    -   the width of the predetermined block 411 being larger than the        height of the current block, e.g. a height of the predetermined        block 411    -   the width of the predetermined block 411 being smaller than the        height of the current block, e.g. a height of the predetermined        block 411

According to this embodiment, if the fourth predetermined criterionwould be fulfilled in either one of the case of the split directionindicated by the split direction flag 518 being horizontal and the caseof the split direction indicated by the split direction flag 518 beingvertical, is non-discriminative between,

-   -   the width of the predetermined block 411 equaling the height of        the current block    -   the width of the predetermined block 411 being larger than the        height of the current block    -   the width of the predetermined block 411 being smaller than the        height of the current block

In other words, in the case of mtt_split_vertical_flag, e.g. the splitdirection flag 518, a configuration may employ two extra contexts forthe cases when the number of possible outcomes for the syntax element isunbalanced. The context modelling, e.g. for the second context, maydepend on the following:

-   -   The current width and height    -   Availability of the binary horizontal and vertical splits (BH        and BV)    -   Availability of the ternary horizontal and vertical splits (TH        and TV)

Table 3, shown in FIG. 21, shows an exemplary context modeling for themtt_split_vertical_flag syntax element, as may be employed for thesecond context for decoding the split direction flag 518. W and Hdescribe the width and height of the current node. BH, TH, BV and TVdescribe the availability of the binary and ternary horizontal andvertical syntax elements. If either BH+TH or BV+TV is equal to 0, thesyntax element's value can be inferred and no context modeling isrequired.

Alternatively, another dependency that may be exploited for bettercontext modelling of the mtt_split_vertical_flag, e.g. the splitdirection flag 518, is the size in relation to the above and leftneighbors. Under the assumption that the block sizes are locallycorrelated, a split that subdivides the block into parts shaped morealike the neighbors might be more probable than other splits. A simpleformulation of this dependency can be implemented based of the followingtwo variables: d₀=w/w_(above), d₁=h/h_(left) (with w and h being currentwidth and height, w_(above) the width of the above neighbor block, andh_(left) the height of the left neighbor block). The alternative contextmodelling for the mtt_split_vertical_flag depends on the following:

-   -   Left and above neighbor availability    -   The current width and height    -   The height of the left neighbor    -   The width of the above neighbor    -   Availability of the binary horizontal and vertical splits (BH        and BV)    -   Availability of the ternary horizontal and vertical splits (TH        and TV)

Table 4, shown in FIG. 22, shows an example of such a context modelingfor the mtt_split_vertical_flag based on split availability and currentblocks shape similarity to neighboring CUs shapes (expressed by d₀ andd₁ as described above). For example, the shown context modelling may beapplied for the second context for decoding the split direction flag518.

Accordingly, according to an embodiment, the second context 552additionally depends on whether, and discriminates between,

-   -   a first ratio between a width of the predetermined block 411 and        a width of a coding block above the predetermined block 411        equaling a second ratio between a height of the current block        and a height of a coding block to the left of the predetermined        block 411    -   the first ratio being larger than the second ratio    -   the first ratio being smaller than the second ratio

According to an embodiment, if the fourth predetermined criterion wouldnot neither be fulfilled in case of a split direction indicated by thesplit direction flag 518 being horizontal nor in case of the splitdirection indicated by the split direction flag 518 being vertical or befulfilled both in case of a split direction indicated by the splitdirection flag 518 being horizontal as well as in case of the splitdirection indicated by the split direction flag 518 being vertical, thesecond context 552, additionally depends on whether, and discriminatesbetween,

-   -   a first ratio between a width of the predetermined block 411 and        a width of a coding block above the predetermined block 411        equaling a second ratio between a height of the current block        and a height of a coding block to the left of the predetermined        block 411    -   the first ratio being larger than the second ratio    -   the first ratio being smaller than the second ratio

According to this embodiment, if the fourth predetermined criterionwould be fulfilled in either one of the case of the split directionindicated by the split direction flag 518 being horizontal and the caseof the split direction indicated by the split direction flag 518 beingvertical, the second context 552, is non-discriminative between,

-   -   a first ratio between a width of the predetermined block 411 and        a width of a coding block above the predetermined block 411        equaling a second ratio between a height of the current block        and a height of a coding block to the left of the predetermined        block 411    -   the first ratio being larger than the second ratio    -   the first ratio being smaller than the second ratio

According to an embodiment, the second context 552 is non-discriminativebetween,

-   -   whether the fourth predetermined criterion would neither be        fulfilled in case of the split direction indicated by the split        direction flag 518 being horizontal nor in case of the split        direction indicated by the split direction flag 518 being        vertical and    -   whether the fourth predetermined criterion would be fulfilled        both in case of a split direction indicated by the split        direction flag 518 being horizontal as well as in case of the        split direction indicated by the split direction flag 518 being        vertical.

According to an embodiment, the apparatus 400;500;600 is configured todecode the triple flag 519 from the data stream 14 by context adaptiveentropy decoding using a third context which depends on a number ofsplits of the recursive multi-tree splitting using which thepredetermined block 411 is obtained, or a size of the predeterminedblock 411.

According to an embodiment, the apparatus 400;500;600 is configured todecode the triple flag 519 from the data stream 14 by context adaptiveentropy decoding using a third context which depends on whether, anddiscriminates between, the split direction flag 518 indicating ahorizontal split direction, and the split direction flag 518 indicatinga vertical split direction.

In other words, a configuration for mtt_split_binary_flag, e.g. thetriple flag 519, may use different context models depending on thepreviously signaled or inferred information (as mtt_split_binary_flagfollows the mtt_split_vertical_flag in both shown binarization schemes,e.g. the schemes shown in FIGS. 11 and 12) and the current partitioningtree state, as summarized in Table 5, shown in FIG. 23. The contextmodeling for the flag, e.g. the triple flag 519, may depends on thefollowing:

-   -   The current BT-depth (number of non-QT splits up to the current        node)        -   Alternatively, BT depth might calculated as follows (in            terms of current QT-depth d_(QT), CTU size W_(CTU) and            current width and height):

d _(BT)=log₂((W _(CTU) W _(CTU))/(W _(curr) H _(curr)))−2·d _(QT)

-   -   The value of the previously signaled or inferred flag        mtt_split_vertical_flag for the current node

Table 5, shown in FIG. 23, shows an exemplarily context modeling for themtt_split_binary_flag syntax element, e.g. the triple flag 519. Thebinary tree depth (BT-depth) describes the number of binary splits orits equivalent of the current node, e.g. the current recursion of therecursive splitting. The value in the row mtt_split_vertical_flagdescribes the value signaled or inferred at the current partitioninglevel prior to the coding of the syntax element mtt_split_binary_flag.

FIG. 8 illustrates an apparatus 800 for decoding a picture 12′ accordingto an embodiment of the present disclosure. For example the apparatus800 may be similar to the decoder 20. The apparatus 800 for decoding apicture 12′ is configured to partition the picture 12′ into codingblocks 425 using recursive multi-tree splitting depending on splittinginformation 415 signaled in a data stream 14, and further, to decode thepicture 12′ from coding information 440 which is signaled in the datastream 14 and relates to the coding blocks 425. The the apparatus 800 isconfigured to partition the picture 12′ into the coding blocks 425depending on splitting information 415 signaled in a data stream 14 bydecoding a split flag 416 and a quad flag 417 of the splittinginformation 415 from the data stream 14, wherein the split flag 416indicates whether a predetermined block 411 of the picture 12′ is to besplit or not to be split thereby stopping the recursive multi-treesplitting with the predetermined block 411 becoming one of the codingblocks 425. The quad flag 417 indicates whether the predetermined block411 of the picture 12′ is to be split into four child blocks 412 or not.If the predetermined block 411 of the picture 12′ is to be split, butnot to be split into four child blocks 412, the partitioning of thepicture 12′ comprises decoding a split direction flag 518 from the datastream 14 which indicates whether the predetermined block 411 of thepicture 12′ is to be split vertically or horizontally, and furthercomprises decoding a triple flag 519 from the data stream 14 whichindicates whether the predetermined block 411 of the picture 12′ is tobe split into three child blocks 412 or into two child blocks 412. Ifthe predetermined block 411 of the picture 12′ is to be split, thepartitioning of the picture 12′ comprises resuming the recursivemulti-tree splitting for the child blocks 412 using even further flagsof the splitting information 415. The apparatus 800 is furtherconfigured to decode the triple flag 519 from the data stream 14 bycontext adaptive entropy decoding using a third context 853 whichdepends on a number of splits of the recursive multi-tree splittingusing which the predetermined block 411 is obtained, or a size of thepredetermined block 411. Additionally or alternatively, the thirdcontext 853 depends on whether, and discriminates between, the splitdirection flag 518 indicating a horizontal split direction, and thesplit direction flag 518 indicating a vertical split direction.

FIG. 9 illustrates an apparatus 900 for decoding a picture 12′ accordingto an embodiment of the present disclosure. For example the apparatus900 may be similar to the decoder 20.40.

-   -   The apparatus 900 is configured to partition the picture 12′        into coding blocks 425 using recursive multi-tree splitting        depending on splitting information 415 signaled in a data stream        14, and further to decode the picture 12′ from coding        information 440 which is signaled in the data stream 14 and        relates to the coding blocks 425. The apparatus 900 is        configured to to partition the picture 12′ into the coding        blocks 425 depending on splitting information 415 signaled in a        data stream 14 by decoding a split flag 416 and a quad flag 417        of the splitting information 415 from the data stream 14,        wherein the split flag 416 indicates whether a predetermined        block 411 of the picture 12′ is to be split or not to be split        thereby stopping the recursive multi-tree splitting with the        predetermined block 411 becoming one of the coding blocks 425.        The quad flag 417 indicates whether the predetermined block 411        of the picture 12′ is to be split into four child blocks 412 or        not. If the predetermined block 411 of the picture 12′ is to be        split, but not to be split into four child blocks 412,        partitioning the picture 12′ comprises decoding one or more        further flags 418 of the splitting information 415 from the data        stream 14 which indicate whether the predetermined block 411 of        the picture 12′ is to be split into two or three child blocks        412 vertically or horizontally. If the predetermined block 411        of the picture 12′ is to be split, partitioning the picture 12′        comprises resuming the recursive multi-tree splitting for the        child blocks 412 using even further flags of the splitting        information 415. The apparatus 900 is further configured to        select one of a first mode and a second mode. Operating in the        first mode, the apparatus 900 is configured to decode the quad        flag 417 after the split flag 416 if the split flag 416        indicates that the predetermined block 411 of the picture 12′ is        to be split. Operating in the second mode, the apparatus 900 is        configured to decode the split flag 416 after the quad flag 417        if the quad flag 417 indicates that the predetermined child        block of the picture 12′ is not to be split into four child        blocks 412.

For example, due to the availability constraints, the existingpartitioning tree, e.g. the tree 1100, already uses an adaptive treestructure. The interchanging of the shape type and the direction alsouses an adaptive partitioning tree. Generally, the ordering of thesyntax elements reflects a fixed probability at each given node.However, the probability varies depending on the signal characteristicand the operation point of the codec. For example, larger quantizationparameters, i.e., low bit rate operation points, tend to results inlarger leaf nodes. In such a case, a split is less probable, hence, theconfiguration in FIG. 12 is advantageous. However, at the other end ofthe operation point, the split information is often positive, hence, theconfiguration in FIG. 11 is advantageous. An adaptive partitioning treeconfiguration would allow both partitioning tree signaling binarizationsand switch between the two options depending on the contextualcharacteristics. An extension would hold several different partitioningtrees and switch among the trees depending on either the neighboringpartitioning trees (backward-adaptive) or a syntax element in at theroot specifies the partitioning tree (forward-adaptive).

Thus, according to an embodiment, the apparatus 900 is configured toperform the selection depending on a mode signalization in the datastream 14. In other words, the selection may be forward-adaptive.

According to an alternative embodiment, the apparatus 900 is configuredto perform the selection backward adaptively.

For example, according to an embodiment, the apparatus 900 is configuredto perform the selection depending on an evaluation of one or more of

-   -   block sizes of a set of previous coding blocks 425, e.g. coding        blocks of the coding block 425 that resulted from a previous        partitioning of a block or a part of the picture 12′, for        example a previously partitioned CTU or a neighboring CTU. For        example, this option may be realized using a sliding window.    -   number of splits from which a set of previously coding blocks        425 results    -   a quantization parameter signaled in the data stream 14

According to embodiments, the syntax elements, e.g. the flags, arecoupled to the depth in terms of the nested partitioning tree. Accordingto further embodiments, a combined depth unifies the information, e.g.the depth information, so that the context modeling for the syntaxelements related to the partitioning tree rely only on a single depthvalue. The most straightforward realization may be a single depth valuethat is increased after each split. Alternatively, the depth may beweighted depending on the split type. For example, a QT depth maycontribute a fixed positive value to the depth counter, whereas a binarysplit only contributes a weighted number of the fixed positive value ofthe quadtree, with the weight w≤1.

According to embodiments, the binary tree and the ternary tree arecoupled, i.e., the direction of the partitioning is signaled firstfollowed by the information whether the resulting partitions are binaryor ternary. In some circumstances, there is a shift in probability forthe direction given the finale shape type. A configuration of thepresented invention may adaptively interchange the two syntax elementsand incorporates the information into the context modeling.

A further extension to the adaptive partitioning tree concept is theadaptive signaling of the shape size, either backward-adaptively orforward-adaptively. For example, when a 16×16 block is binary horizontalsplit, the result can be a 16×4 and a 16×12 shapes, or two 16×8 shapes.In the current VVC draft, the final ratio is fixed. A configuration thatexploits the shape size can analyze the neighboring partition trees anddecide which shape size should be used. Note that the extension is thesame as additional partition trees that are available in the case on anadaptive partitioning scheme.

The features and embodiments described in the context of a decoder, mayequally applied in an encoder. Accordingly, embodiments provide anapparatus for encoding a picture, for example the apparatus 1300illustrated in FIG. 13. The apparatus 1300 for encoding a picture 12 isconfigured to partition the picture 12 into coding blocks 425 usingrecursive multi-tree splitting. The encoder is configured to encodesplitting information 415 defining the partitioning in a data stream 14.Further, the apparatus 1300 is configured to encode the picture 12 intocoding information 440 which relates to the coding blocks 425 and encodethe coding information 440 in the data stream 14. The recursivemulti-tree splitting for partitioning the picture 12 into the codingblocks 425 may be performed by any embodiment of the recursivemulti-tree splitting as described with respect to the decoders400;500;600;800;900, that is, the coding blocks 425 may be provided bysaid recursive multi-tree splitting. Similarly, the splittinginformation may be provided by the recursive multi-tree splitting. Thenumber and the type of flags, the encoder 1300 encodes for obtaining thesplitting information 415 may depend on the respective embodiment of therecursive splitting. For example, the encoding of the splittinginformation 415 is specific to a current recursion of the recursivesplitting, depending on a partitioning of a predetermined block 411which is subject to the current recursion of the recursive splitting.That is, referring to the embodiments of the recursive splittingdescribed with respect to the decoders 400;500;600;800;900, whenever thepartitioning of the picture 12 implies a decoding of a predeterminedflag, the apparatus 1300 is configured for encoding the predeterminedflag into the data stream 14. For example, whenever the partitioning orthe picture implies to infer a predetermined flag, the encoder is notnecessarily configured to encode the predetermined flag, but may beconfigured to suppress an encoding of the predetermined flag.

FIG. 14 shows a flow chart of a method 1400 for decoding a picture 12′according to an embodiment. For example, method 1400 may be performed bythe apparatus 400. The method comprises partitioning 1401 the picture12′ into coding blocks 425 using recursive multi-tree splittingdepending on splitting information 415 signaled in a data stream 14. Themethod 1400 further comprises a step 1402 of decoding the picture 12′from coding information 440 which is signaled in the data stream 14 andrelates to the coding blocks 425. The step 1401 comprises decoding asplit flag 416 of the splitting information 415 from the data stream 14which indicates whether a predetermined block 411 of the picture 12′ isto be split or not to be split thereby stopping the recursive multi-treesplitting with the predetermined block 411 becoming one of the codingblocks 425. The step 1401 further comprises a step 1420, which isperformed if the split flag 416 indicates that the predetermined block411 of the picture 12′ is to be split. The step 1420 comprises a step1430 of decoding a quad flag 417 of the splitting information 415 fromthe data stream 14 which indicates whether the predetermined block 411of the picture 12′ is to be split into four child blocks 412 or not. Thestep 1420 further comprises a step 1431, which is performed if the quadflag 417 indicates that the predetermined block 411 of the picture 12′is not to be split into four child blocks 412. The step 1431 comprisesdecoding one or more further flags 418 of the splitting information 415from the data stream 14 which indicate whether the predetermined block411 of the picture 12′ is to be split into two or three child blocks 412vertically or horizontally. The step 1420 further comprises resuming therecursive multi-tree splitting for the child blocks 412 using evenfurther flags of the splitting information 415.

FIG. 15 shows a flow chart of a method 1500 for decoding a picture 12′according to an embodiment. For example, method 1500 may be performed bythe apparatus 500. The method comprises partitioning 1501 the picture12′ into coding blocks 425 using recursive multi-tree splittingdepending on splitting information 415 signaled in a data stream 14. Themethod 1500 further comprises step 1402. The step 1501 comprises a step1511 of decoding a split flag 416 and a quad flag 417 of the splittinginformation 415 from the data stream 14, wherein the split flag 416indicates whether a predetermined block 411 of the picture 12′ is to besplit or not to be split thereby stopping the recursive multi-treesplitting with the predetermined block 411 becoming one of the codingblocks 425, and the quad flag 417 indicates whether the predeterminedblock 411 of the picture 12′ is to be split into four child blocks 412or not. The step 1501 further comprises a step 1521, which is performedif the predetermined block 411 of the picture 12′ is to be split, butnot to be split into four child blocks 412. The step 1521 comprises thestep 1533 of decoding a split direction flag 518 from the data stream 14which indicates whether the predetermined block 411 of the picture 12′is to be split vertically or horizontally, if neither a second nor athird predetermined criterion is fulfilled. The decoding 1533 of thesplit direction flag 518 uses a second context 552 which depends onwhether, and discriminates between,

-   -   the fourth predetermined criterion would not neither be        fulfilled in case of a split direction indicated by the split        direction flag 518 being horizontal nor in case of the split        direction indicated by the split direction flag 518 being        vertical or be fulfilled both in case of a split direction        indicated by the split direction flag 518 being horizontal as        well as in case of the split direction indicated by the split        direction flag 518 being vertical    -   the fourth predetermined criterion would be fulfilled in case of        the split direction indicated by the split direction flag 518        being horizontal and not be fulfilled in case of the split        direction indicated by the split direction flag 518 being        vertical    -   the fourth predetermined criterion would not be fulfilled in        case of the split direction indicated by the split direction        flag 518 being horizontal and be fulfilled in case of the split        direction indicated by the split direction flag 518 being        vertical

The step 1521 further comprises the step 1534 of inferring that thesplit direction flag 518 indicates that the predetermined block 411 ofthe picture 12′ is to be split vertically, if the second predeterminedcriterion is fulfilled. The step 1521 further comprises the step 1535 ofinferring that the split direction flag 518 indicates that thepredetermined block 411 of the picture 12′ is to be split horizontally,if the third predetermined criterion is fulfilled. The step 1521 furthercomprises the step 1536 of decoding a triple flag 519 from the datastream 14 which indicates whether the predetermined block 411 of thepicture 12′ is to be split into three child blocks 412 or into two childblocks 412, if a fourth predetermined criterion is not fulfilled. Thestep 1521 further comprises the step 1537 of inferring that the tripleflag 519 indicates that the predetermined block 411 of the picture 12′is to be split into two child blocks 412, if the fourth predeterminedcriterion is fulfilled. The step 1501 further comprises the step 1503.The step 1503 performs step 1403, if the predetermined block 411 of thepicture 12′ is to be split.

FIG. 16 shows a flow chart of a method 1600 for decoding a picture 12′according to an embodiment. For example, method 1600 may be performed bythe apparatus 600. The method comprises partitioning 1601 the picture12′ into coding blocks 425 using recursive multi-tree splittingdepending on splitting information 415 signaled in a data stream 14. Themethod 1600 further comprises the step 1402. The step 1601 comprises thestep 1511. The step 1601 further comprises a step 1622 which isperformed if the predetermined block 411 of the picture 12′ is to besplit, but not to be split into four child blocks 412. The step 1622comprises the steps 1661, 1534, 1535, 1536 and 1662. The step 1661comprises decoding a split direction flag 518 from the data stream 14which indicates whether the predetermined block 411 of the picture 12′is to be split vertically or horizontally, if neither a second nor athird predetermined criterion is fulfilled. The decoding 1661 of thesplit direction flag 518 comprises using a second context 552. Theconfiguration of the second context 552 as used by the method 1600 orthe apparatus 600 may differ from the configuration of the secondcontext 552 as used by the method 1500 or the apparatus 500. In case ofthe method 1600 and the apparatus 600, the second context depends onwhether, and discriminates between:

-   -   a first number of criteria among the fourth and fifth        predetermined criteria which would be fulfilled in case of a        split direction indicated by the split direction flag 518 being        horizontal equals a second number of criteria among the fourth        and fifth predetermined criteria which would be fulfilled in        case of the split direction indicated by the split direction        flag 518 being vertical    -   the first number being greater than the second number    -   the first number being smaller than the second number

The step 1662 comprises inferring that the triple flag 519 indicatesthat the predetermined block 411 of the picture 12′ is to be split intotwo child blocks 412, if the fourth predetermined criterion isfulfilled, and that the triple flag 519 indicates that the predeterminedblock 411 of the picture 12′ is to be split into three child blocks 412and suppress the decoding of the triple flag 519 from the data stream14, if a fifth predetermined criterion is fulfilled. Step 1601 furthercomprises the step 1503.

FIG. 17 shows a flow chart of a method 1800 for decoding a picture 12′according to an embodiment. For example, method 1800 may be performed bythe apparatus 800. The method comprises partitioning 1801 the picture12′ into coding blocks 425 using recursive multi-tree splittingdepending on splitting information 415 signaled in a data stream 14. Themethod 1800 further comprises the step 1402. The step 1801 comprises thestep 1511. The step 1801 further comprises a step 1823 which isperformed if the predetermined block 411 of the picture 12′ is to besplit, but not to be split into four child blocks 412. The step 1823comprises the step 1881 of decoding a split direction flag 518 from thedata stream 14 which indicates whether the predetermined block 411 ofthe picture 12′ is to be split vertically or horizontally. The step 1823further comprises the step 1882 of decoding a triple flag 519 from thedata stream 14 which indicates whether the predetermined block 411 ofthe picture 12′ is to be split into three child blocks 412 or into twochild blocks 412. Step 1801 further comprises the step 1503.

FIG. 18 shows a flow chart of a method 1900 for decoding a picture 12′according to an embodiment. For example, method 1900 may be performed bythe apparatus 900. The method comprises partitioning 1901 the picture12′ into coding blocks 425 using recursive multi-tree splittingdepending on splitting information 415 signaled in a data stream 14. Themethod 1900 further comprises the step 1402. The step 1901 comprises thestep 1911 decoding a split flag 416 and a quad flag 417 of the splittinginformation 415 from the data stream 14, wherein the split flag 416indicates whether a predetermined block 411 of the picture 12′ is to besplit or not to be split thereby stopping the recursive multi-treesplitting with the predetermined block 411 becoming one of the codingblocks 425, and the quad flag 417 indicates whether the predeterminedblock 411 of the picture 12′ is to be split into four child blocks 412or not. The step 1901 further comprises a step 1905 of selecting one ofa first mode and a second mode. In the first mode, the method 1900comprises, for example during the step 1911, decoding the quad flag 417after the split flag 416 if the split flag 416 indicates that thepredetermined block 411 of the picture 12′ is to be split. In the secondmode, the method 1900 comprises, for example during the step 1911,decoding the split flag 416 after the quad flag 417 if the quad flag 417indicates that the predetermined child block of the picture 12′ is notto be split into four child blocks 412. The step 1901 comprises a step1991, which is performed if the predetermined block 411 of the picture12′ is to be split, but not to be split into four child blocks 412. Thestep 1991 comprises decoding one or more further flags 418 of thesplitting information 415 from the data stream 14 which indicate whetherthe predetermined block 411 of the picture 12′ is to be split into twoor three child blocks 412 vertically or horizontally. The step 1901further comprises the step 1503.

Further embodiments provide methods for encoding a picture 12. Themethods for encoding a picture comprise partitioning of the picture 12into coding blocks 425 using recursive multi-tree splitting and aencoding of splitting information 415 defining the partitioning in adata stream 14. The methods further comprise a encoding of the picture12 into coding information 440 which relates to the coding blocks 425and encode the coding information 440 in the data stream 14. Similarlyto the correspondence between the encoders and the decoders describedabove, the methods for encoding a picture resemble the methods 1400,1500, 1600, 1800, 1900. For example, the partitioning of the picture 12relies on the same steps as described with respect to these methods.That is, whenever a flag is to be decoded, the methods for encodingcomprise encoding the respective flag. Steps of the methods 1400, 1500,1600, 1800, 1900 that comprise inferring a flag, are not necessarilypart of the method for encoding a picture, but, instead, the methods maycomprise suppressing an encoding of the flag.

Although some aspects have been described in the context of anapparatus, it is clear that these aspects also represent a descriptionof the corresponding method, where a block or device corresponds to amethod step or a feature of a method step. Analogously, aspectsdescribed in the context of a method step also represent a descriptionof a corresponding block or item or feature of a correspondingapparatus.

Some or all of the method steps may be executed by (or using) a hardwareapparatus, like for example, a microprocessor, a programmable computeror an electronic circuit. In some embodiments, one or more of the mostimportant method steps may be executed by such an apparatus.

Depending on certain implementation requirements, embodiments of theinvention can be implemented in hardware or in software or at leastpartially in hardware or at least partially in software. Theimplementation can be performed using a digital storage medium, forexample a floppy disk, a DVD, a Blu-Ray, a CD, a ROM, a PROM, an EPROM,an EEPROM or a FLASH memory, having electronically readable controlsignals stored thereon, which cooperate (or are capable of cooperating)with a programmable computer system such that the respective method isperformed. Therefore, the digital storage medi-um may be computerreadable.

Some embodiments according to the invention comprise a data carrierhaving electroni-cally readable control signals, which are capable ofcooperating with a programmable computer system, such that one of themethods described herein is performed.

Generally, embodiments of the present invention can be implemented as acomputer program product with a program code, the program code beingoperative for performing one of the methods when the computer programproduct runs on a computer. The program code may for example be storedon a machine readable carrier.

Other embodiments comprise the computer program for performing one ofthe methods described herein, stored on a machine readable carrier.

In other words, an embodiment of the inventive method is, therefore, acomputer program having a program code for performing one of the methodsdescribed herein, when the computer program runs on a computer.

A further embodiment of the inventive methods is, therefore, a datacarrier (or a digital storage medium, or a computer-readable medium)comprising, recorded thereon, the computer program for performing one ofthe methods described herein. The data carrier, the digital storagemedium or the recorded medium are typically tangible and/ornon-transitory.

A further embodiment of the inventive method is, therefore, a datastream or a sequence of signals representing the computer program forperforming one of the methods de-scribed herein. The data stream or thesequence of signals may for example be configured to be transferred viaa data communication connection, for example via the Internet.

A further embodiment comprises a processing means, for example acomputer, or a programmable logic device, configured to or adapted toperform one of the methods de-scribed herein.

A further embodiment comprises a computer having installed thereon thecomputer pro-gram for performing one of the methods described herein.

A further embodiment according to the invention comprises an apparatusor a system configured to transfer (for example, electronically oroptically) a computer program for performing one of the methodsdescribed herein to a receiver. The receiver may, for exam-ple, be acomputer, a mobile device, a memory device or the like. The apparatus orsys-tem may, for example, comprise a file server for transferring thecomputer program to the receiver.

In some embodiments, a programmable logic device (for example a fieldprogrammable gate array) may be used to perform some or all of thefunctionalities of the methods de-scribed herein. In some embodiments, afield programmable gate array may cooperate with a microprocessor inorder to perform one of the methods described herein. Generally, themethods are advantageously performed by any hardware apparatus.

The apparatus described herein may be implemented using a hardwareapparatus, or using a computer, or using a combination of a hardwareapparatus and a computer.

The methods described herein may be performed using a hardwareapparatus, or using a computer, or using a combination of a hardwareapparatus and a computer.

While this invention has been described in terms of several embodiments,there are alterations, permutations, and equivalents which fall withinthe scope of this invention. It should also be noted that there are manyalternative ways of implementing the methods and compositions of thepresent invention. It is therefore intended that the following appendedclaims be interpreted as including all such alterations, permutationsand equivalents as fall within the true spirit and scope of the presentinvention.

1. Apparatus for decoding a picture, configured to partition the pictureinto coding blocks using recursive multi-tree splitting depending onsplitting information signaled in a data stream, decode the picture fromcoding information which is signaled in the data stream and relates tothe coding blocks, wherein the apparatus is configured to partition thepicture into the coding blocks depending on splitting informationsignaled in a data stream by decoding a split flag and a quad flag ofthe splitting information from the data stream, wherein the split flagindicates whether a predetermined block of the picture is to be split ornot to be split thereby stopping the recursive multi-tree splitting withthe predetermined block becoming one of the coding blocks, and the quadflag indicates whether the predetermined block of the picture is to besplit into four child blocks or not, if the predetermined block of thepicture is to be split, but not to be split into four child blocks,decoding a split direction flag from the data stream which indicateswhether the predetermined block of the picture is to be split verticallyor horizontally, if neither a second nor a third predetermined criterionis fulfilled, inferring that the split direction flag indicates that thepredetermined block of the picture is to be split vertically, if thesecond predetermined criterion is fulfilled, and inferring that thesplit direction flag indicates that the predetermined block of thepicture is to be split horizontally, if the third predeterminedcriterion is fulfilled, decoding a triple flag from the data streamwhich indicates whether the predetermined block of the picture is to besplit into three child blocks or into two child blocks, if a fourthpredetermined criterion is not fulfilled, and inferring that the tripleflag indicates that the predetermined block of the picture is to besplit into two child blocks, if the fourth predetermined criterion isfulfilled, and that the triple flag indicates that the predeterminedblock of the picture is to be split into three child blocks and suppressthe decoding of the triple flag from the data stream, if a fifthpredetermined criterion is fulfilled, if the predetermined block of thepicture is to be split, resuming the recursive multi-tree splitting forthe child blocks using even further flags of the splitting information,decode the split direction flag from the data stream by context adaptiveentropy decoding using a second context which depends on whether, anddiscriminates between, a first number of criteria among the fourth andfifth predetermined criteria which would be fulfilled in case of a splitdirection indicated by the split direction flag being horizontal equalsa second number of criteria among the fourth and fifth predeterminedcriteria which would be fulfilled in case of the split directionindicated by the split direction flag being vertical, the first numberbeing greater than the second number, and the first number being smallerthan the second number.
 2. Apparatus of claim 1, wherein the secondcontext additionally depends on whether, and discriminates between, awidth of the predetermined block equaling a height of the current block,and the width of the predetermined block being larger than the height ofthe current block, and the width of the predetermined block beingsmaller than the height of the current block.
 3. Apparatus of claim 1,wherein the second context, if the fourth predetermined criterion wouldnot neither be fulfilled in case of a split direction indicated by thesplit direction flag being horizontal nor in case of the split directionindicated by the split direction flag being vertical or be fulfilledboth in case of a split direction indicated by the split direction flagbeing horizontal as well as in case of the split direction indicated bythe split direction flag being vertical, additionally depends onwhether, and discriminates between, a width of the predetermined blockequaling a height of the current block, and the width of thepredetermined block being larger than the height of the current block,and the width of the predetermined block being smaller than the heightof the current block, and if the fourth predetermined criterion would befulfilled in either one of the case of the split direction indicated bythe split direction flag being horizontal and the case of the splitdirection indicated by the split direction flag being vertical, isnon-discriminative between, the width of the predetermined blockequaling the height of the current block, and the width of thepredetermined block being larger than the height of the current block,and the width of the predetermined block being smaller than the heightof the current block.
 4. Apparatus of claim 1, wherein the secondcontext, if the fourth predetermined criterion would not neither befulfilled in case of a split direction indicated by the split directionflag being horizontal nor in case of the split direction indicated bythe split direction flag being vertical or be fulfilled both in case ofa split direction indicated by the split direction flag being horizontalas well as in case of the split direction indicated by the splitdirection flag being vertical, additionally depends on whether, anddiscriminates between, a first ratio between a width of thepredetermined block and a width of a coding block above thepredetermined block equaling a second ratio between a height of thecurrent block and a height of a coding block to the left of thepredetermined block, and the first ratio being larger than the secondratio, and the first ratio being smaller than the second ratio, if thefourth predetermined criterion would be fulfilled in either one of thecase of the split direction indicated by the split direction flag beinghorizontal and the case of the split direction indicated by the splitdirection flag being vertical, is non-discriminative between, a firstratio between a width of the predetermined block and a width of a codingblock above the predetermined block equaling a second ratio between aheight of the current block and a height of a coding block to the leftof the predetermined block, and the first ratio being larger than thesecond ratio, and the first ratio being smaller than the second ratio.5. Apparatus of claim 1, wherein the second context isnon-discriminative between, whether the fourth predetermined criterionwould neither be fulfilled in case of the split direction indicated bythe split direction flag being horizontal nor in case of the splitdirection indicated by the split direction flag being vertical andwhether the fourth predetermined criterion would be fulfilled both incase of a split direction indicated by the split direction flag beinghorizontal as well as in case of the split direction indicated by thesplit direction flag being vertical.
 6. Apparatus of claim 1, configuredto decode the triple flag from the data stream by context adaptiveentropy decoding using a third context which depends on, a number ofsplits of the recursive multi-tree splitting using which thepredetermined block is acquired, or a size of the predetermined block.7. Apparatus of claim 1, configured to decode the triple flag from thedata stream by context adaptive entropy decoding using a third contextwhich depends on whether, and discriminates between, the split directionflag indicating a horizontal split direction, and the split directionflag indicating a vertical split direction.
 8. Apparatus for decoding apicture, configured to partition the picture into coding blocks usingrecursive multi-tree splitting depending on splitting informationsignaled in a data stream, decode the picture from coding informationwhich is signaled in the data stream and relates to the coding blocks,wherein the apparatus is configured to partition the picture into thecoding blocks depending on splitting information signaled in a datastream by decoding a split flag and a quad flag of the splittinginformation from the data stream, wherein the split flag indicateswhether a predetermined block of the picture is to be split or not to besplit thereby stopping the recursive multi-tree splitting with thepredetermined block becoming one of the coding blocks, and the quad flagindicates whether the predetermined block of the picture is to be splitinto four child blocks or not, if the predetermined block of the pictureis to be split, but not to be split into four child blocks, decoding asplit direction flag from the data stream which indicates whether thepredetermined block of the picture is to be split vertically orhorizontally, if neither a second nor a third predetermined criterion isfulfilled, inferring that the split direction flag indicates that thepredetermined block of the picture is to be split vertically, if thesecond predetermined criterion is fulfilled, and inferring that thesplit direction flag indicates that the predetermined block of thepicture is to be split horizontally, if the third predeterminedcriterion is fulfilled, decoding a triple flag from the data streamwhich indicates whether the predetermined block of the picture is to besplit into three child blocks or into two child blocks, if a fourthpredetermined criterion is not fulfilled, and inferring that the tripleflag indicates that the predetermined block of the picture is to besplit into two child blocks, if the fourth predetermined criterion isfulfilled, if the predetermined block of the picture is to be split,resuming the recursive multi-tree splitting for the child blocks usingeven further flags of the splitting information, decode the splitdirection flag from the data stream by context adaptive entropy decodingusing a second context which depends on whether, and discriminatesbetween, the fourth predetermined criterion would not neither befulfilled in case of a split direction indicated by the split directionflag being horizontal nor in case of the split direction indicated bythe split direction flag being vertical or be fulfilled both in case ofa split direction indicated by the split direction flag being horizontalas well as in case of the split direction indicated by the splitdirection flag being vertical, the fourth predetermined criterion wouldbe fulfilled in case of the split direction indicated by the splitdirection flag being horizontal and not be fulfilled in case of thesplit direction indicated by the split direction flag being vertical,and the fourth predetermined criterion would not be fulfilled in case ofthe split direction indicated by the split direction flag beinghorizontal and be fulfilled in case of the split direction indicated bythe split direction flag being vertical.
 9. Apparatus of claim 8,wherein the second context additionally depends on whether, anddiscriminates between, a width of the predetermined block equaling aheight of the current block, and the width of the predetermined blockbeing larger than the height of the current block, and the width of thepredetermined block being smaller than the height of the current block.10. Apparatus of claim 8, wherein the second context, if the fourthpredetermined criterion would not neither be fulfilled in case of asplit direction indicated by the split direction flag being horizontalnor in case of the split direction indicated by the split direction flagbeing vertical or be fulfilled both in case of a split directionindicated by the split direction flag being horizontal as well as incase of the split direction indicated by the split direction flag beingvertical, additionally depends on whether, and discriminates between, awidth of the predetermined block equaling a height of the current block,and the width of the predetermined block being larger than the height ofthe current block, and the width of the predetermined block beingsmaller than the height of the current block, and if the fourthpredetermined criterion would be fulfilled in either one of the case ofthe split direction indicated by the split direction flag beinghorizontal and the case of the split direction indicated by the splitdirection flag being vertical, is non-discriminative between, the widthof the predetermined block equaling the height of the current block, andthe width of the predetermined block being larger than the height of thecurrent block, and the width of the predetermined block being smallerthan the height of the current block.
 11. Apparatus of claim 8, whereinthe second context additionally depends on whether, and discriminatesbetween, a first ratio between a width of the predetermined block and awidth of a coding block above the predetermined block equaling a secondratio between a height of the current block and a height of a codingblock to the left of the predetermined block, and the first ratio beinglarger than the second ratio, and the first ratio being smaller than thesecond ratio.
 12. Apparatus of claim 8, wherein the second context, ifthe fourth predetermined criterion would not neither be fulfilled incase of a split direction indicated by the split direction flag beinghorizontal nor in case of the split direction indicated by the splitdirection flag being vertical or be fulfilled both in case of a splitdirection indicated by the split direction flag being horizontal as wellas in case of the split direction indicated by the split direction flagbeing vertical, additionally depends on whether, and discriminatesbetween, a first ratio between a width of the predetermined block and awidth of a coding block above the predetermined block equaling a secondratio between a height of the current block and a height of a codingblock to the left of the predetermined block, and the first ratio beinglarger than the second ratio, and the first ratio being smaller than thesecond ratio, if the fourth predetermined criterion would be fulfilledin either one of the case of the split direction indicated by the splitdirection flag being horizontal and the case of the split directionindicated by the split direction flag being vertical, isnon-discriminative between, a first ratio between a width of thepredetermined block and a width of a coding block above thepredetermined block equaling a second ratio between a height of thecurrent block and a height of a coding block to the left of thepredetermined block, and the first ratio being larger than the secondratio, and the first ratio being smaller than the second ratio. 13.Apparatus of claim 8, wherein the second context is non-discriminativebetween, whether the fourth predetermined criterion would neither befulfilled in case of the split direction indicated by the splitdirection flag being horizontal nor in case of the split directionindicated by the split direction flag being vertical and whether thefourth predetermined criterion would be fulfilled both in case of asplit direction indicated by the split direction flag being horizontalas well as in case of the split direction indicated by the splitdirection flag being vertical.
 14. Apparatus of claim 8, configured todecode the triple flag from the data stream by context adaptive entropydecoding using a third context which depends on, a number of splits ofthe recursive multi-tree splitting using which the predetermined blockis acquired, or a size of the predetermined block.
 15. Apparatus ofclaim 8, configured to decode the triple flag from the data stream bycontext adaptive entropy decoding using a third context which depends onwhether, and discriminates between, the split direction flag indicatinga horizontal split direction, and the split direction flag indicating avertical split direction.
 16. Apparatus for encoding a picture,configured to partition the picture into coding blocks using recursivemulti-tree splitting and encode splitting information defining thepartitioning in a data stream, encode the picture into codinginformation which is signaled in the data stream and relates to thecoding blocks and encode the coding information in the data stream,wherein the apparatus is configured to partition the picture into thecoding blocks depending on splitting information signaled in a datastream by encoding a split flag and a quad flag of the splittinginformation into the data stream, wherein the split flag indicateswhether a predetermined block of the picture is to be split or not to besplit thereby stopping the recursive multi-tree splitting with thepredetermined block becoming one of the coding blocks, and the quad flagindicates whether the predetermined block of the picture is to be splitinto four child blocks or not, if the predetermined block of the pictureis to be split, but not to be split into four child blocks, encoding asplit direction flag into the data stream which indicates whether thepredetermined block of the picture is to be split vertically orhorizontally, if neither a second nor a third predetermined criterion isfulfilled, suppress the encoding of the split direction flag if thesecond predetermined criterion is fulfilled wherein same is to beinferred to indicate that predetermined block of the picture is to besplit vertically, if the second predetermined criterion is fulfilled,and suppress the encoding of the split direction flag if the thirdpredetermined criterion is fulfilled wherein same is to be inferred toindicate that the predetermined block of the picture is to be splithorizontally, if the third predetermined criterion is fulfilled,encoding a triple flag into the data stream which indicates whether thepredetermined block of the picture is to be split into three childblocks or into two child blocks, if fourth and fifth predeterminedcriteria are not fulfilled, and suppress the encoding the triple flag ifthe fourth predetermined criterion is fulfilled wherein same is to beinferred to indicate that the predetermined block of the picture is tobe split into two child blocks, if the fourth predetermined criterion isfulfilled, and suppress the encoding the triple flag if the fifthpredetermined criterion is fulfilled, wherein the triple flag is to beinferred to indicate that the predetermined block of the picture is tobe split into three child blocks, if the fifth predetermined criterionis fulfilled, if the predetermined block of the picture is to be split,resuming the encoding the splitting information for the child blocksusing even further flags of the splitting information, encode the splitdirection flag into the data stream by context adaptive entropy encodingusing a second context which depends on whether, and discriminatesbetween, a first number of criteria among the fourth and fifthpredetermined criteria which would be fulfilled in case of a splitdirection indicated by the split direction flag being horizontal equalsa second number of criteria among the fourth and fifth predeterminedcriteria which would be fulfilled in case of the split directionindicated by the split direction flag being vertical, the first numberbeing greater than the second number, and the first number being smallerthan the second number.
 17. Apparatus for encoding a picture, configuredto partition the picture into coding blocks using recursive multi-treesplitting and encode splitting information defining the partitioning ina data stream, encode the picture into coding information which relatesto the coding blocks and encode the coding information in the datastream, wherein the apparatus is configured to encode the splittinginformation in the data stream by encoding a split flag and a quad flagof the splitting information into the data stream, wherein the splitflag indicates whether a predetermined block of the picture is to besplit or not to be split thereby stopping the recursive multi-treesplitting with the predetermined block becoming one of the codingblocks, and the quad flag indicates whether the predetermined block ofthe picture is to be split into four child blocks or not, if thepredetermined block of the picture is to be split, but not to be splitinto four child blocks, encoding a split direction flag into the datastream which indicates whether the predetermined block of the picture isto be split vertically or horizontally, if neither a second nor a thirdpredetermined criterion is fulfilled, suppress the encoding of the splitdirection flag if the second predetermined criterion is fulfilledwherein same is to be inferred to indicate that predetermined block ofthe picture is to be split vertically, if the second predeterminedcriterion is fulfilled, and suppress the encoding of the split directionflag if the third predetermined criterion is fulfilled wherein same isto be inferred to indicate that the predetermined block of the pictureis to be split horizontally, if the third predetermined criterion isfulfilled, encoding a triple flag into the data stream which indicateswhether the predetermined block of the picture is to be split into threechild blocks or into two child blocks, if a fourth predeterminedcriterion is not fulfilled, and suppress the encoding the triple flag ifthe fourth predetermined criterion is fulfilled wherein same is to beinferred to indicate that the predetermined block of the picture is tobe split into two child blocks, if the fourth predetermined criterion isfulfilled, if the predetermined block of the picture is to be split,resuming the encoding of the splitting information for the child blocksusing even further flags of the splitting information, encode the splitdirection flag into the data stream by context adaptive entropy encodingusing a second context which depends on whether, and discriminatesbetween, the fourth predetermined criterion would not neither befulfilled in case of a split direction indicated by the split directionflag being horizontal nor in case of the split direction indicated bythe split direction flag being vertical or be fulfilled both in case ofa split direction indicated by the split direction flag being horizontalas well as in case of the split direction indicated by the splitdirection flag being vertical, the fourth predetermined criterion wouldbe fulfilled in case of the split direction indicated by the splitdirection flag being horizontal and not be fulfilled in case of thesplit direction indicated by the split direction flag being vertical,and the fourth predetermined criterion would not be fulfilled in case ofthe split direction indicated by the split direction flag beinghorizontal and be fulfilled in case of the split direction indicated bythe split direction flag being vertical.
 18. Method for decoding apicture, comprising: partitioning the picture into coding blocks usingrecursive multi-tree splitting depending on splitting informationsignaled in a data stream, decoding the picture from coding informationwhich is signaled in the data stream and relates to the coding blocks,wherein the method comprises partitioning the picture into the codingblocks depending on splitting information signaled in a data stream bydecoding a split flag and a quad flag of the splitting information fromthe data stream, wherein the split flag indicates whether apredetermined block of the picture is to be split or not to be splitthereby stopping the recursive multi-tree splitting with thepredetermined block becoming one of the coding blocks, and the quad flagindicates whether the predetermined block of the picture is to be splitinto four child blocks or not, if the predetermined block of the pictureis to be split, but not to be split into four child blocks, decoding asplit direction flag from the data stream which indicates whether thepredetermined block of the picture is to be split vertically orhorizontally, if neither a second nor a third predetermined criterion isfulfilled, inferring that the split direction flag indicates that thepredetermined block of the picture is to be split vertically, if thesecond predetermined criterion is fulfilled, and inferring that thesplit direction flag indicates that the predetermined block of thepicture is to be split horizontally, if the third predeterminedcriterion is fulfilled, decoding a triple flag from the data streamwhich indicates whether the predetermined block of the picture is to besplit into three child blocks or into two child blocks, if a fourthpredetermined criterion is not fulfilled, and inferring that the tripleflag indicates that the predetermined block of the picture is to besplit into two child blocks, if the fourth predetermined criterion isfulfilled, and that the triple flag indicates that the predeterminedblock of the picture is to be split into three child blocks and suppressthe decoding of the triple flag from the data stream, if a fifthpredetermined criterion is fulfilled, if the predetermined block of thepicture is to be split, resuming the recursive multi-tree splitting forthe child blocks using even further flags of the splitting information,decoding the split direction flag from the data stream by contextadaptive entropy decoding using a second context which depends onwhether, and discriminates between, a first number of criteria among thefourth and fifth predetermined criteria which would be fulfilled in caseof a split direction indicated by the split direction flag beinghorizontal equals a second number of criteria among the fourth and fifthpredetermined criteria which would be fulfilled in case of the splitdirection indicated by the split direction flag being vertical, thefirst number being greater than the second number, and the first numberbeing smaller than the second number.
 19. A non-transitory digitalstorage medium having a computer program stored thereon to perform themethod for decoding a picture, the method comprising: partitioning thepicture into coding blocks using recursive multi-tree splittingdepending on splitting information signaled in a data stream, decodingthe picture from coding information which is signaled in the data streamand relates to the coding blocks, wherein the method comprisespartitioning the picture into the coding blocks depending on splittinginformation signaled in a data stream by decoding a split flag and aquad flag of the splitting information from the data stream, wherein thesplit flag indicates whether a predetermined block of the picture is tobe split or not to be split thereby stopping the recursive multi-treesplitting with the predetermined block becoming one of the codingblocks, and the quad flag indicates whether the predetermined block ofthe picture is to be split into four child blocks or not, if thepredetermined block of the picture is to be split, but not to be splitinto four child blocks, decoding a split direction flag from the datastream which indicates whether the predetermined block of the picture isto be split vertically or horizontally, if neither a second nor a thirdpredetermined criterion is fulfilled, inferring that the split directionflag indicates that the predetermined block of the picture is to besplit vertically, if the second predetermined criterion is fulfilled,and inferring that the split direction flag indicates that thepredetermined block of the picture is to be split horizontally, if thethird predetermined criterion is fulfilled, decoding a triple flag fromthe data stream which indicates whether the predetermined block of thepicture is to be split into three child blocks or into two child blocks,if a fourth predetermined criterion is not fulfilled, and inferring thatthe triple flag indicates that the predetermined block of the picture isto be split into two child blocks, if the fourth predetermined criterionis fulfilled, and that the triple flag indicates that the predeterminedblock of the picture is to be split into three child blocks and suppressthe decoding of the triple flag from the data stream, if a fifthpredetermined criterion is fulfilled, if the predetermined block of thepicture is to be split, resuming the recursive multi-tree splitting forthe child blocks using even further flags of the splitting information,decoding the split direction flag from the data stream by contextadaptive entropy decoding using a second context which depends onwhether, and discriminates between, a first number of criteria among thefourth and fifth predetermined criteria which would be fulfilled in caseof a split direction indicated by the split direction flag beinghorizontal equals a second number of criteria among the fourth and fifthpredetermined criteria which would be fulfilled in case of the splitdirection indicated by the split direction flag being vertical, thefirst number being greater than the second number, and the first numberbeing smaller than the second number, when said computer program is runby a computer.
 20. Method for decoding a picture, comprisingpartitioning the picture into coding blocks using recursive multi-treesplitting depending on splitting information signaled in a data stream,decoding the picture from coding information which is signaled in thedata stream and relates to the coding blocks, wherein the methodcomprises partitioning the picture into the coding blocks depending onsplitting information signaled in a data stream by decoding a split flagand a quad flag of the splitting information from the data stream,wherein the split flag indicates whether a predetermined block of thepicture is to be split or not to be split thereby stopping the recursivemulti-tree splitting with the predetermined block becoming one of thecoding blocks, and the quad flag indicates whether the predeterminedblock of the picture is to be split into four child blocks or not, ifthe predetermined block of the picture is to be split, but not to besplit into four child blocks, decoding a split direction flag from thedata stream which indicates whether the predetermined block of thepicture is to be split vertically or horizontally, if neither a secondnor a third predetermined criterion is fulfilled, inferring that thesplit direction flag indicates that the predetermined block of thepicture is to be split vertically, if the second predetermined criterionis fulfilled, and inferring that the split direction flag indicates thatthe predetermined block of the picture is to be split horizontally, ifthe third predetermined criterion is fulfilled, decoding a triple flagfrom the data stream which indicates whether the predetermined block ofthe picture is to be split into three child blocks or into two childblocks, if a fourth predetermined criterion is not fulfilled, andinferring that the triple flag indicates that the predetermined block ofthe picture is to be split into two child blocks, if the fourthpredetermined criterion is fulfilled, if the predetermined block of thepicture is to be split, resuming the recursive multi-tree splitting forthe child blocks using even further flags of the splitting information,decoding the split direction flag from the data stream by contextadaptive entropy decoding using a second context which depends onwhether, and discriminates between, the fourth predetermined criterionwould not neither be fulfilled in case of a split direction indicated bythe split direction flag being horizontal nor in case of the splitdirection indicated by the split direction flag being vertical or befulfilled both in case of a split direction indicated by the splitdirection flag being horizontal as well as in case of the splitdirection indicated by the split direction flag being vertical, thefourth predetermined criterion would be fulfilled in case of the splitdirection indicated by the split direction flag being horizontal and notbe fulfilled in case of the split direction indicated by the splitdirection flag being vertical, and the fourth predetermined criterionwould not be fulfilled in case of the split direction indicated by thesplit direction flag being horizontal and be fulfilled in case of thesplit direction indicated by the split direction flag being vertical.21. A non-transitory digital storage medium having a computer programstored thereon to perform the method for decoding a picture, said methodcomprising partitioning the picture into coding blocks using recursivemulti-tree splitting depending on splitting information signaled in adata stream, decoding the picture from coding information which issignaled in the data stream and relates to the coding blocks, whereinthe method comprises partitioning the picture into the coding blocksdepending on splitting information signaled in a data stream by decodinga split flag and a quad flag of the splitting information from the datastream, wherein the split flag indicates whether a predetermined blockof the picture is to be split or not to be split thereby stopping therecursive multi-tree splitting with the predetermined block becoming oneof the coding blocks, and the quad flag indicates whether thepredetermined block of the picture is to be split into four child blocksor not, if the predetermined block of the picture is to be split, butnot to be split into four child blocks, decoding a split direction flagfrom the data stream which indicates whether the predetermined block ofthe picture is to be split vertically or horizontally, if neither asecond nor a third predetermined criterion is fulfilled, inferring thatthe split direction flag indicates that the predetermined block of thepicture is to be split vertically, if the second predetermined criterionis fulfilled, and inferring that the split direction flag indicates thatthe predetermined block of the picture is to be split horizontally, ifthe third predetermined criterion is fulfilled, decoding a triple flagfrom the data stream which indicates whether the predetermined block ofthe picture is to be split into three child blocks or into two childblocks, if a fourth predetermined criterion is not fulfilled, andinferring that the triple flag indicates that the predetermined block ofthe picture is to be split into two child blocks, if the fourthpredetermined criterion is fulfilled, if the predetermined block of thepicture is to be split, resuming the recursive multi-tree splitting forthe child blocks using even further flags of the splitting information,decoding the split direction flag from the data stream by contextadaptive entropy decoding using a second context which depends onwhether, and discriminates between, the fourth predetermined criterionwould not neither be fulfilled in case of a split direction indicated bythe split direction flag being horizontal nor in case of the splitdirection indicated by the split direction flag being vertical or befulfilled both in case of a split direction indicated by the splitdirection flag being horizontal as well as in case of the splitdirection indicated by the split direction flag being vertical, thefourth predetermined criterion would be fulfilled in case of the splitdirection indicated by the split direction flag being horizontal and notbe fulfilled in case of the split direction indicated by the splitdirection flag being vertical, and the fourth predetermined criterionwould not be fulfilled in case of the split direction indicated by thesplit direction flag being horizontal and be fulfilled in case of thesplit direction indicated by the split direction flag being vertical,when said computer program is run by a computer.
 22. Method for encodinga picture, comprising partitioning the picture into coding blocks usingrecursive multi-tree splitting and encoding splitting informationdefining the partitioning in a data stream, encoding the picture intocoding information which is signaled in the data stream and relates tothe coding blocks and encode the coding information in the data stream,wherein the method comprises partitioning the picture into the codingblocks depending on splitting information signaled in a data stream byencoding a split flag and a quad flag of the splitting information intothe data stream, wherein the split flag indicates whether apredetermined block of the picture is to be split or not to be splitthereby stopping the recursive multi-tree splitting with thepredetermined block becoming one of the coding blocks, and the quad flagindicates whether the predetermined block of the picture is to be splitinto four child blocks or not, if the predetermined block of the pictureis to be split, but not to be split into four child blocks, encoding asplit direction flag into the data stream which indicates whether thepredetermined block of the picture is to be split vertically orhorizontally, if neither a second nor a third predetermined criterion isfulfilled, suppressing the encoding of the split direction flag if thesecond predetermined criterion is fulfilled wherein same is to beinferred to indicate that predetermined block of the picture is to besplit vertically, if the second predetermined criterion is fulfilled,and suppressing the encoding of the split direction flag if the thirdpredetermined criterion is fulfilled wherein same is to be inferred toindicate that the predetermined block of the picture is to be splithorizontally, if the third predetermined criterion is fulfilled,encoding a triple flag into the data stream which indicates whether thepredetermined block of the picture is to be split into three childblocks or into two child blocks, if fourth and fifth predeterminedcriteria are not fulfilled, and suppressing the encoding the triple flagif the fourth predetermined criterion is fulfilled wherein same is to beinferred to indicate that the predetermined block of the picture is tobe split into two child blocks, if the fourth predetermined criterion isfulfilled, and suppressing the encoding the triple flag if the fifthpredetermined criterion is fulfilled, wherein the triple flag is to beinferred to indicate that the predetermined block of the picture is tobe split into three child blocks, if the fifth predetermined criterionis fulfilled, if the predetermined block of the picture is to be split,resuming the encoding the splitting information for the child blocksusing even further flags of the splitting information, encoding thesplit direction flag into the data stream by context adaptive entropyencoding using a second context which depends on whether, anddiscriminates between, a first number of criteria among the fourth andfifth predetermined criteria which would be fulfilled in case of a splitdirection indicated by the split direction flag being horizontal equalsa second number of criteria among the fourth and fifth predeterminedcriteria which would be fulfilled in case of the split directionindicated by the split direction flag being vertical, the first numberbeing greater than the second number, and the first number being smallerthan the second number.
 23. Data stream encoded by a method according toclaim
 22. 24. A non-transitory digital storage medium having a computerprogram stored thereon to perform the method for encoding a picture,said method comprising partitioning the picture into coding blocks usingrecursive multi-tree splitting and encoding splitting informationdefining the partitioning in a data stream, encoding the picture intocoding information which is signaled in the data stream and relates tothe coding blocks and encode the coding information in the data stream,wherein the method comprises partitioning the picture into the codingblocks depending on splitting information signaled in a data stream byencoding a split flag and a quad flag of the splitting information intothe data stream, wherein the split flag indicates whether apredetermined block of the picture is to be split or not to be splitthereby stopping the recursive multi-tree splitting with thepredetermined block becoming one of the coding blocks, and the quad flagindicates whether the predetermined block of the picture is to be splitinto four child blocks or not, if the predetermined block of the pictureis to be split, but not to be split into four child blocks, encoding asplit direction flag into the data stream which indicates whether thepredetermined block of the picture is to be split vertically orhorizontally, if neither a second nor a third predetermined criterion isfulfilled, suppressing the encoding of the split direction flag if thesecond predetermined criterion is fulfilled wherein same is to beinferred to indicate that predetermined block of the picture is to besplit vertically, if the second predetermined criterion is fulfilled,and suppressing the encoding of the split direction flag if the thirdpredetermined criterion is fulfilled wherein same is to be inferred toindicate that the predetermined block of the picture is to be splithorizontally, if the third predetermined criterion is fulfilled,encoding a triple flag into the data stream which indicates whether thepredetermined block of the picture is to be split into three childblocks or into two child blocks, if fourth and fifth predeterminedcriteria are not fulfilled, and suppressing the encoding the triple flagif the fourth predetermined criterion is fulfilled wherein same is to beinferred to indicate that the predetermined block of the picture is tobe split into two child blocks, if the fourth predetermined criterion isfulfilled, and suppressing the encoding the triple flag if the fifthpredetermined criterion is fulfilled, wherein the triple flag is to beinferred to indicate that the predetermined block of the picture is tobe split into three child blocks, if the fifth predetermined criterionis fulfilled, if the predetermined block of the picture is to be split,resuming the encoding the splitting information for the child blocksusing even further flags of the splitting information, encoding thesplit direction flag into the data stream by context adaptive entropyencoding using a second context which depends on whether, anddiscriminates between, a first number of criteria among the fourth andfifth predetermined criteria which would be fulfilled in case of a splitdirection indicated by the split direction flag being horizontal equalsa second number of criteria among the fourth and fifth predeterminedcriteria which would be fulfilled in case of the split directionindicated by the split direction flag being vertical, the first numberbeing greater than the second number, and the first number being smallerthan the second number, when said computer program is run by a computer.25. Method for encoding a picture, comprising partitioning the pictureinto coding blocks using recursive multi-tree splitting and encodingsplitting information defining the partitioning in a data stream,encoding the picture into coding information which relates to the codingblocks and encode the coding information in the data stream, wherein themethod comprises encoding the splitting information in the data streamby encoding a split flag and a quad flag of the splitting informationinto the data stream, wherein the split flag indicates whether apredetermined block of the picture is to be split or not to be splitthereby stopping the recursive multi-tree splitting with thepredetermined block becoming one of the coding blocks, and the quad flagindicates whether the predetermined block of the picture is to be splitinto four child blocks or not, if the predetermined block of the pictureis to be split, but not to be split into four child blocks, encoding asplit direction flag into the data stream which indicates whether thepredetermined block of the picture is to be split vertically orhorizontally, if neither a second nor a third predetermined criterion isfulfilled, suppress the encoding of the split direction flag if thesecond predetermined criterion is fulfilled wherein same is to beinferred to indicate that predetermined block of the picture is to besplit vertically, if the second predetermined criterion is fulfilled,and suppressing the encoding of the split direction flag if the thirdpredetermined criterion is fulfilled wherein same is to be inferred toindicate that the predetermined block of the picture is to be splithorizontally, if the third predetermined criterion is fulfilled,encoding a triple flag into the data stream which indicates whether thepredetermined block of the picture is to be split into three childblocks or into two child blocks, if a fourth predetermined criterion isnot fulfilled, and suppressing the encoding the triple flag if thefourth predetermined criterion is fulfilled wherein same is to beinferred to indicate that the predetermined block of the picture is tobe split into two child blocks, if the fourth predetermined criterion isfulfilled, if the predetermined block of the picture is to be split,resuming the encoding of the splitting information for the child blocksusing even further flags of the splitting information, encoding thesplit direction flag into the data stream by context adaptive entropyencoding using a second context which depends on whether, anddiscriminates between, the fourth predetermined criterion would notneither be fulfilled in case of a split direction indicated by the splitdirection flag being horizontal nor in case of the split directionindicated by the split direction flag being vertical or be fulfilledboth in case of a split direction indicated by the split direction flagbeing horizontal as well as in case of the split direction indicated bythe split direction flag being vertical, the fourth predeterminedcriterion would be fulfilled in case of the split direction indicated bythe split direction flag being horizontal and not be fulfilled in caseof the split direction indicated by the split direction flag beingvertical, and the fourth predetermined criterion would not be fulfilledin case of the split direction indicated by the split direction flagbeing horizontal and be fulfilled in case of the split directionindicated by the split direction flag being vertical.
 26. Data streamencoded by a method according to claim
 25. 27. A non-transitory digitalstorage medium having a computer program stored thereon to perform themethod of for encoding a picture, said method comprising partitioningthe picture into coding blocks using recursive multi-tree splitting andencoding splitting information defining the partitioning in a datastream, encoding the picture into coding information which relates tothe coding blocks and encode the coding information in the data stream,wherein the method comprises encoding the splitting information in thedata stream by encoding a split flag and a quad flag of the splittinginformation into the data stream, wherein the split flag indicateswhether a predetermined block of the picture is to be split or not to besplit thereby stopping the recursive multi-tree splitting with thepredetermined block becoming one of the coding blocks, and the quad flagindicates whether the predetermined block of the picture is to be splitinto four child blocks or not, if the predetermined block of the pictureis to be split, but not to be split into four child blocks, encoding asplit direction flag into the data stream which indicates whether thepredetermined block of the picture is to be split vertically orhorizontally, if neither a second nor a third predetermined criterion isfulfilled, suppress the encoding of the split direction flag if thesecond predetermined criterion is fulfilled wherein same is to beinferred to indicate that predetermined block of the picture is to besplit vertically, if the second predetermined criterion is fulfilled,and suppressing the encoding of the split direction flag if the thirdpredetermined criterion is fulfilled wherein same is to be inferred toindicate that the predetermined block of the picture is to be splithorizontally, if the third predetermined criterion is fulfilled,encoding a triple flag into the data stream which indicates whether thepredetermined block of the picture is to be split into three childblocks or into two child blocks, if a fourth predetermined criterion isnot fulfilled, and suppressing the encoding the triple flag if thefourth predetermined criterion is fulfilled wherein same is to beinferred to indicate that the predetermined block of the picture is tobe split into two child blocks, if the fourth predetermined criterion isfulfilled, if the predetermined block of the picture is to be split,resuming the encoding of the splitting information for the child blocksusing even further flags of the splitting information, encoding thesplit direction flag into the data stream by context adaptive entropyencoding using a second context which depends on whether, anddiscriminates between, the fourth predetermined criterion would notneither be fulfilled in case of a split direction indicated by the splitdirection flag being horizontal nor in case of the split directionindicated by the split direction flag being vertical or be fulfilledboth in case of a split direction indicated by the split direction flagbeing horizontal as well as in case of the split direction indicated bythe split direction flag being vertical, the fourth predeterminedcriterion would be fulfilled in case of the split direction indicated bythe split direction flag being horizontal and not be fulfilled in caseof the split direction indicated by the split direction flag beingvertical, and the fourth predetermined criterion would not be fulfilledin case of the split direction indicated by the split direction flagbeing horizontal and be fulfilled in case of the split directionindicated by the split direction flag being vertical, when said computerprogram is run by a computer.